Biomedical subjects

D Hanson

Publications and source records attributed to D Hanson.

At least 19 recordsLinked to original sources

PubMed2006

Broadband dielectric function of nonequilibrium warm dense gold.

We report on the first single-state measurement of the broadband (450-800 nm) dielectric function of gold isochorically heated by a femtosecond laser pulse to energy densities of 10(6) - 10(7) J/kg. A Drude and an interband component are clearly seen in the imaginary part of the dielectric function. The Drude component increases with energy density while the interband component shows both enhancement and redshift. This is in strong disagreement with predictions of a recent calculation of dielectric function based on limited Brillouin zone sampling.

Journal Article↗

PubMed2005

Localized versus regional hyperthermia: comparison of xenotransplants treated with a small animal ultrasound system and waterbath limb immersion.

The response of xenotransplants were compared with waterbath immersion vs focal ultrasound (US) hyperthermia using tumour growth delay, immunhistochemistry and histopathology assays. Waterbath hyperthermia was performed by limb immersion. Precautions were taken to minimize total body heating by surrounding the mouse with plastic insulators. Thermometry was performed with clinical-grade, 20-gauge needle thermocouples and monitored with a Labthermics unit. Significant differences in cytotoxicity between ultrasound and waterbath treatment of tumors at 43 degrees C were observed as determined by TUNNEL assay. Conversely, contralateral (non-treated) tumours in animals treated with similar temperature demonstrated no significant differences between modalities. Western blot analysis revealed increased hsp70 induction at 43 degrees C in waterbath vs focal ultrasound hyperthermia. Comparison of tumour growth delay between tumours heated with waterbath vs ultrasound at 43 degrees C but not at 41 degrees C revealed significant differences. This is the first study comparing localized vs regional hyperthermia using the small animal ultrasound system (SAHUS) delivery system. Consistent ultrasound hyperthermia can be achieved throughout a xenotransplant. At equivalent temperature of 43 degrees C for 60?min, waterbath hyperthermia demonstrated greater local response vs ultrasound hyperthermia.

Animals↗

PubMed2000

Bactericidal and tumoricidal activities of synthetic peptides derived from granulysin.

Granulysin, a 9-kDa protein localized to human CTL and NK cell granules, is cytolytic against tumor cells and microbes. Molecular modeling predicts that granulysin is composed of five alpha-helices separated by short loop regions. In this report, synthetic peptides corresponding to the linear granulysin sequence were characterized for lytic activity. Peptides corresponding to the central region of granulysin lyse bacteria, human cells, and synthetic liposomes, while peptides corresponding to the amino or carboxyl regions are not lytic. Peptides corresponding to either helix 2 or helix 3 lyse bacteria, while lysis of human cells and liposomes is dependent on the helix 3 sequence. Peptides in which positively charged arginine residues are substituted with neutral glutamine exhibit reduced lysis of all three targets. While reduction of recombinant 9-kDa granulysin increases lysis of Jurkat cells, reduction of cysteine-containing granulysin peptides decreases lysis of Jurkat cells. In contrast, lysis of bacteria by recombinant granulysin or by cysteine-containing granulysin peptides is unaffected by reducing conditions. Jurkat cells transfected with either CrmA or Bcl-2 are protected from lysis by recombinant granulysin or the peptides. Differential activity of granulysin peptides against tumor cells and bacteria may be exploited to develop specific antibiotics without toxicity for mammalian cells.

Adjuvants, Immunologic↗

PubMed2000

Epidemiology of human immunodeficiency virus-associated opportunistic infections in the United States in the era of highly active antiretroviral therapy.

The incidence of nearly all AIDS-defining opportunistic infections (OIs) decreased significantly in the United States during 1992-1998; decreases in the most common OIs (Pneumocystis carinii pneumonia ¿PCP, esophageal candidiasis, and disseminated Mycobacterium avium complex ¿MAC disease) were more pronounced in 1996-1998, during which time highly active antiretroviral therapy (HAART) was introduced into medical care. Those OIs that continue to occur do so at low CD4+ T lymphocyte counts, and persons whose CD4+ counts have increased in response to HAART are at low risk for OIs, a circumstance that suggests a high degree of immune reconstitution associated with HAART. PCP, the most common serious OI, continues to occur primarily in persons not previously receiving medical care. The most profound effect on survival of patients with AIDS is conferred by HAART, but specific OI prevention measures (prophylaxis against PCP and MAC and vaccination against Streptococcus pneumoniae) are associated with a survival benefit, even when they coincide with the administration of HAART. Continued monitoring of incidence trends and detection of new syndromes associated with HAART are important priorities in the HAART era.

AIDS-Related Opportunistic Infections↗

PubMed2000

Consensual validation of clinical practice model practice guidelines.

Clinical Practice Model (CPM) Practice Guidelines facilitate the delivery of consistent, high-quality patient care by clarifying nursing services and supporting the practice and documentation of each step of the nursing process. CPM Practice Guidelines are unique because they are part of an integrated interactive systems thinking framework to support professional practice; they are reviewed and improved routinely using multiple sources of data and are used by hundreds of nurses daily throughout the United States and Canada. Guidelines are developed using a rigorous standardized format and process. Consensual validation is an important part of establishing and maintaining the credibility of these Guidelines.

Humans↗

PubMed2000

A modular software system for computer-aided surgery and its first application in oral implantology.

Development of complex software applications in image guided therapy (IGT) is often complicated by the fact that providing basic functionality for image processing and user interaction from a graphical user interfaces (GUI) requires considerable manpower for software development. We present a programming environment that combines the high-level image processing library AVW, in-house developed patient-to-image registration procedures, and an interface to position measurement hardware. A specific application can be developed by using Tcl/Tk, a simple platform-independent scripting language, for GUI development. This environment was applied to developing VISIT, a navigation system for computer-aided implant dentistry. VISIT is presented as a result of this paper. Parts of the development environment were made accessible to the public. Future work includes the implementation of video input for connecting ultrasound or fluoroscopy units. We conclude that our approach is well suited to accelerate the development of exploratory new applications of IGT.

Dental Implantation↗

PubMed2000

Effects of dehydration on phonation in excised canine larynges.

The effects of exposure to dry air on phonation were measured in an ex vivo model of vocal fold vibration. Excised canine larynges were mounted on an apparatus and made to phonate at a constant subglottal pressure by means of unhumidified airflow. The phonation threshold pressure (PTP), glottal airflow, sound intensity of the acoustic output, and effects on vocal efficiency were also assessed. Student's t-test was performed on the results. In 17 larynges, the average PTP increased from 10.0 cm H2O to 15.0 cm H2O after exposure to dry airflow (p < .001). In addition, the average flow increased from 585 mL/s to 801 mL/s at a constant suprathreshold subglottal pressure (p < .001), and from 323 mL/s to 610 mL/s at the PTP (p < .001). The average acoustic output levels, measured during stable phonation segments, markedly decreased with exposure to the dry airflow, from 91.5 dB to 88.5 dB (p < .001). The average vocal efficiency decreased from 3.63 x 10(-4) to 7.00 x 10(-5) (p < .001). No such changes were seen in control larynges phonated with 100% humidified air used for driving the airflow. The results support previously reported modeling and experimental findings that dehydration of the vocal fold generally degrades laryngeal performance.

Animals↗

PubMed1999

Aerodynamic measurements of patients with Parkinson's disease.

Patients with Parkinson's disease commonly complain of voice dysfunction. Most of these complaints can be attributed to the known muscular control disorders that occur with Parkinson's disease. However, the manifestations of Parkinson's disease muscular dysfunction on parameters of phonation such as airflow, laryngeal resistance, and subglottal pressure necessary to sustain phonation have not been reported. The purpose of this study was to examine the aerodynamic characteristics of flow, laryngeal resistance, and phonation pressure threshold in a heterogeneous population of patients with Parkinson's disease who had varying voice complaints and to compare the data to similar studies for human subjects who have no voice complaints. The studies used a noninvasive method of detecting flow and acoustic signal from the lips, oral cavity and nose during phonation and used an external flow interruption technique to estimate subglottal pressure and phonation threshold pressure. About one third of the patients could not produce phonation at regular and loud intensities that were comfortable for normal subjects. The mean subglottal pressure (SGP) of patients with Parkinson disease who could produce 3 levels of intensity comparable to normal subjects was significantly higher than the mean SGPs for normal subjects for the same intensities of vocal production. The mean flow rates measured from patients with Parkinson's disease at the same 3 intensities of phonation was not significantly greater than in normal subjects. This indicated that the mean laryngeal resistance calculated for patients with Parkinson's disease was notably and significantly greater than mean laryngeal resistance calculated for normal subjects at the same intensity levels. The mean vocal efficiency (VE) for normal subjects was not significantly different than the mean VE for patients with Parkinson's disease, because greater pressure was used to generate similar flow and acoustic energy. These findings correlate with the perception of patients with Parkinson's disease that they are working harder to produce phonation. The observation of notably greater laryngeal resistance and phonation threshold pressure in patients with Parkinson's disease suggests that further studies of the glottic aperture in patients with Parkinson' disease may be useful for understanding how this common motor disorder disturbs phonation.

Aged↗

PubMed1999

The effects of rehydration on phonation in excised canine larynges.

Experiments using excised canine larynges were conducted to study the restoration of vocal efficiency in dehydrated larynges. Excised larynges were dehydrated with warm, dry air to the point that airflow through the approximated vocal folds would not entrain the folds to produce phonation. The dehydrated vocal folds were then bathed in a saline solution. The rehydrated larynges were then remounted on the bench apparatus that enabled phonation with a constant humidified airflow, and measurements were made of phonation threshold pressure, glottal airflow, and amplitude. Hydration resulted in significantly increased efficiency and decrease in phonation threshold pressure. The findings confirm clinical impressions that hydration is critical in the physiology of normal phonation.

Animals↗

PubMed1999

Split flexor pollicus longus tendon transfer for stabilization of the thumb interphalangeal joint: a cadaveric and clinical study.

The split flexor pollicus longus (FPL) tendon transfer is a surgical technique using the radial half of the FPL tendon rerouted dorsally and inserted into the extensor pollicis longus tendon for correction of Froment's sign. A cadaveric model was designed to investigate the effects of the split FPL tendon transfer on pinch strength. Pinch strength was compared for extrinsic thumb flexion (1) without the split FPL and (2) with the split FPL, tensioned at 3 different positions (0 degrees flexion, 30 degrees flexion, and 60 degrees flexion). We report the clinical results of key pinch strength using split FPL tendon transfer as part of thumb reconstruction for 12 thumbs in 10 patients at an average follow-up time of 2 years. The cadaveric study showed no significant difference in pinch force between specimens with or without split FPL transfer or when comparing tensioning at 0 degrees versus 30 degrees versus 60 degrees. Froment's sign wa s reproduced in all cadavers with pinch activation without split FPL transfer and was eliminated in all specimens after the split FPL transfer. In the clinical portion of this study 12 transfers in 10 patients had an average follow-up pinch strength of 33.7 N (range, 18-80 N) and no evidence of Froment's sign. We conclude that the split FPL tendon transfer is an effective method for correction of Froment's sign due to intrinsic paralysis of the thumb.

Adult↗

PubMed1999

Phonation threshold pressure measurements during phonation by airflow interruption.

OBJECTIVE/HYPOTHESIS: Most methods to measure phonation threshold pressure (PTP) are clinically impractical because they are invasive. This report concerns an airflow interruption system developed to allow noninvasive estimation of (PTP) at different levels of vocal intensity. An estimation of PTP was made for normal subjects with normal larynges and no voice complaints and for individuals who had dysphonia associated with vocal polyps to compare the estimated minimal pressure across the glottis that was required to sustain phonation in the two conditions. STUDY DESIGN: This was a methodological study designed to measure an unanticipated PTP from a subject. METHODS: Subjects sustained a constant tone and the airflow was directed into a section of pipe with an airtight mask over the mouth and nose. The airflow, intramask pressure, and intensity of the acoustic output were recorded. A PTP was predicted from a difference between an estimate of the subglottal pressure and the vocal tract pressure at the point that phonation ceased after interruption of airflow. Eleven control subjects and 13 patients with vocal fold polyps were studied. In each population there were eight men and five women. The individuals in the group with vocal fold polyps averaged 39 years of age, and the control subject group averaged 49 years of age. Normal subjects produced a steady vowel /a/ at 75, 80, and 85 dB. Patients with polyps were unable to sustain phonation at these levels but were able to produce phonation at 65, 70, and 75 dB. The validity of the system was tested using a laryngeal model and in a patient with a normal larynx and voice who had a tracheotomy (placed for sleep apnea syndrome) which allowed direct measurement of subglottal pressure. RESULTS: The measured mean PTP levels (with standard deviation [SD]) for the control subjects were 2.38 (1.273), 2.67 (1.879), and 2.98 (2.23) cm H2O at 75, 80, and 85 dB, respectively. The measured mean PTP levels (with SD) for the patients with polyps were 4.79 (2.67), 5.85 (2.34), and 7.37 (3.26) cm H2O at 75, 80, and 85 dB, respectively. The differences in mean PTP between groups at 75, 80, and 85 dB were significant at P = .013, P = .017, and P = .010, respectively. CONCLUSIONS: The estimations of PTP for patients with vocal fold polyps were significantly higher than for the control subjects at three phonation levels.

Adult↗

PubMed1999

Effect of dietary phosphorus on finishing steer performance, bone status, and carcass maturity.

Yearling crossbred steers (n = 60; 386 kg) were individually fed in a completely randomized experimental design to determine their P requirement. Treatments were in a factorial arrangement with two levels of Ca (.35 or .70% of DM) and five concentrations of P (.14, .19, .24, .29, or .34% of DM). The finishing diet consisted of 34.5% dry-rolled corn, 22.5% brewers grits, 22.5% corn bran, 7.5% ground corncobs, 5% molasses, 3% fat, and 5% supplement. Supplemental P was provided as monosodium phosphate and Ca as limestone. Ash content was determined on the first phalanx bone from the lower front legs following slaughter, and rib bone breaking strength was determined with an Instron Universal Testing Machine. Carcass maturity and shear force were also evaluated on wholesale rib cuts. Because no interactions between Ca and P levels were detected, only main effects are presented. Daily gain, DMI, and feed efficiency were not affected by dietary P concentration or P intake. Bone ash (g or g/100 kg BW) and rib bone breaking strength were also unaffected by dietary P. Feeding .7% Ca decreased (P<.06) ADG and efficiency compared with feeding .35% Ca. Neither dietary Ca nor P had a significant effect on tenderness (shear force), skeletal maturity, or overall maturity. These results indicate that the P requirement for finishing yearlings is .14% of diet DM or less and that supplementing P above levels supplied by basal ingredients in many grain-based finishing diets is not necessary.

Animals↗

PubMed1998

Lymphatic drainage after lumbar surgery.

STUDY DESIGN: A case report of lymphatic drainage after anterior retroperitoneal debridement and reconstruction for lumbar osteomyelitis. OBJECTIVES: To report a case of protracted lymphatic drainage after anterior lumbar surgery, a complication that has not been reported previously. SUMMARY OF BACKGROUND DATA: Lymphatic drainage after transthoracic surgery is a well-recognized complication. The possibility of lymphatic drainage after anterior lumbar surgery is less likely to be considered. METHODS: The cause, clinical symptoms and appearance, treatment, and differential diagnosis are reviewed. RESULTS: Lymphangiography is useful in diagnosis and should be performed early if the diagnosis is in doubt. Percutaneous drainage can facilitate early wound healing. CONCLUSION: Lymphatic drainage should be considered in the differential diagnosis of postoperative wound drainage, particularly after surgical debridement for osteomyelitis.

Adult↗

PubMed1998

Genetic and physical localization of the root-knot nematode resistance locus mi in tomato.

As part of a map-based cloning strategy designed to isolate the root-knot nematode resistance gene Mi, tomato F2 populations were analyzed in order to identify recombination points close to this economically important gene. A total of 21,089 F2 progeny plants were screened using morphological markers. An additional 1887 F2 were screened using PCR-based flanking markers. Fine-structure mapping of recombinants with newly developed AFLP markers, and RFLP markers derived from physically mapped cosmid subclones, localized Mi to a genomic region of about 550 kb. The low frequency of recombinants indicated that recombination was generally suppressed in these crosses and that crossovers were restricted to particular regions. To circumvent this problem, a population of Lycopersicon peruvianum, the species from which Mi was originally introgressed, that was segregating for resistance was developed. Screening of this population with PCR, RFLP and AFLP markers identified several plants with crossovers near Mi. Recombination frequency was approximately eight-fold higher in the Mi region of the L. peruvianum cross. However, even within the wild species cross, recombination sites were not uniformly distributed in the region. By combining data from the L. esculentum and L. peruvianum recombinant analyses, it was possible to localize Mi to a region of the genome spanning less than 65 kb.

Animals↗

PubMed1998

Subtraction ictal SPET co-registered to MRI in partial epilepsy: description and technical validation of the method with phantom and patient studies.

Computer-aided subtraction of the co-registered and normalized interictal from the ictal single photon emission tomography (SPET) scan, followed by co-registration to the magnetic resonance image, may improve the utility of ictal SPET in the localization of partial epilepsy. This paper describes and technically validates our method. The SPET to SPET co-registration was tested using six sequential 99Tc(m) brain phantom SPET images of different known positions (15 matches). The registration error was determined by multiplying the calculated match transformation matrix by the inverse of the known transformation matrix. The 'worst case' co-registration error was less that one voxel diameter in all cases (median 3.2 mm, range 1.2-4.8 mm). For interictal to ictal SPET registrations in 10 consecutive intractable partial epilepsy patients, a similar root mean square distance (RMSD) between corresponding points on the matched scans was found as for the phantom studies (median 2.2 vs 2.6 mm). The appropriateness of our normalization was studied by comparing the pixel intensity distributions between the matched scans, and by analysing the subtraction pixel intensity distribution. The pixel intensity distribution for both the normalized phantom, and paired normalized patient studies, were closely matched to each other except for the extreme values, which in clinical situations likely represent regions of ictal activation or depression. The subtraction image intensity distributions were symmetrically centred on zero for all values up to at least within the 5th to 95th centile range, confirming good normalization for the 'non-activated' pixels. Also, a linear relationship was demonstrated between the measured pixel intensity on the phantom scans and the true changes in 99Tc(m) activity based on its decay constant. The results of this study demonstrate that our method produces accurate SPET to SPET co-registration, and appropriate SPET normalization, thereby allowing a valid ictal subtraction image to be derived.

Brain↗

PubMed1998

Subtraction ictal SPECT co-registered to MRI improves clinical usefulness of SPECT in localizing the surgical seizure focus.

Traditional side-by-side visual interpretation of ictal and interictal single-photon emission computed tomography (SPECT) scans can be difficult in identifying the surgical focus, particularly in patients with extratemporal or otherwise unlocalized intractable epilepsy. Computer-aided subtraction ictal SPECT co-registered to MRI (SISCOM) may improve the clinical usefulness of SPECT in localizing the surgical seizure focus. We studied 51 consecutive intractable partial epilepsy patients who had interictal and ictal scans. The SPECT studies were blindly reviewed and classified as either localizing to 1 of 16 sites in the brain or as nonlocalizing. SISCOM images were localizing in 45 of 51 (88.2%) compared with 20 of 51 (39.2%) for traditional side-by-side inspection of ictal and interictal SPECT images (p < 0.0001). Inter-rater agreement for two independent reviewers was better for SISCOM (84.3% versus 41.2%, kappa = 0.83 versus 0.26; p < 0.0001). Concordance of seizure localization with the more established tests was also higher for SISCOM. Late injection of the radiotracer (> 45 seconds), but not secondary generalization of the seizure, was associated with a falsely localizing or nonlocalizing SISCOM. Epilepsy surgery patients whose SISCOM localization was concordant with a falsely localizing or nonlocalizing SISCOM. Epilepsy surgery patients whose SISCOM localization was concordant with the surgical site were more likely to have excellent outcome than patients with nonconcordant or nonlocalizing findings (62.5% [10/16] versus 20% [2/10]; p < 0.05). On the other hand, seizure localization by the traditional method of SPECT inspection had no significant association with postsurgical outcome. We conclude that SISCOM improves the sensitivity and the specificity of SPECT in localizing the seizure focus for epilepsy surgery. Concordance between SISCOM localization and site of surgery is predictive of postsurgical improvement in seizure outcome.

Brain↗

PubMed1997

Intrinsic balancing in reconstruction of the tetraplegic hand.

This article reviews 183 hand reconstructions in 135 consecutive tetraplegic patients. Comparisons were made between 103 extrinsic reconstructions with intrinsic balancing procedures and 80 extrinsic reconstructions without intrinsic balancing procedures. Extrinsic reconstructions (tendon transfers and tenodesis in the forearm muscles) were augmented by intrinsic reconstructive procedures (tendon transfers or tenodesis to improve the intrinsic balance of the fingers) in patients exhibiting digital imbalance. Intrinsic procedures included primarily the flexor digitorum superficialis (FDS) lasso procedure or the intrinsic tenodesis procedure. The patients were stratified by level of spinal cord injury and by type of extrinsic and intrinsic reconstruction. Hands reconstructed with intrinsic balancing versus without intrinsic balancing, as well as intrinsic balancing using a FDS lasso procedure versus an intrinsic tenodesis procedure, were compared with patients with the same level of spinal cord function. Patients who underwent reconstructions with intrinsic balancing had more grip strength, by an average of 13-26 N, than those who did not undergo intrinsic balancing. When different intrinsic procedures were compared, there was improvement in grip strength and function in activities of daily living for all hands, but there was no significant difference between FDS lasso or intrinsic tenodesis procedures. The indications for intrinsic balancing during extrinsic reconstruction are developed into treatment algorithms based on the senior author's surgical experience. The authors recommended that digital intrinsic procedures be included in hand reconstruction for tetraplegic patients exhibiting intrinsic imbalance to help improve digital function and provide increased grip strength.

Adolescent↗

PubMed1996

Pressure ulcer incidence in an acute care setting.

The purpose of this prospective study was to determine the incidence of pressure ulcers and to examine factors related to pressure ulcer development in patients in an acute care setting. Adult medical and surgical patients who were free of pressure ulcers at admission were assessed within 36 hours of admission and then three times per week for 2 weeks or until discharge. Instruments included a demographic data form, a skin assessment form, and the Braden Scale for Predicting Pressure Sore Risk. Most subjects had 46 assessments completed. The sample consisted of 149 subjects, with a pressure ulcer incidence rate of 13.4% (n = 20). Subjects who acquired pressure ulcers had lower hemoglobin levels (t = 2.17, p = 0.03), spent more time in bed (t = 3.90, p = 0.0001), and spent less time in a chair (t = 3.2, p = 0.002) than those who did not acquire pressure ulcers. A stepwise logistic regression analysis was used to calculate risk of pressure ulcer development. In the final model, hemoglobin level and hours spent in bed continued to be predictors of pressure ulcer development (chi 2 = 9.306, df = 2, p = 0.0095). All 20 subjects who acquired pressure ulcers were further categorized into groups with stage I (n = 12) or stage II (n = 8) ulcers. Patients with stage I pressure ulcers were primarily receiving post-surgical care (67%), whereas patients who acquired stage II ulcers had medical conditions that affected tissue perfusion, such as respiratory diseases (50%) and diabetes mellitus (12%).

Acute Disease↗