Biomedical subjects
B Johnson
Publications and source records attributed to B Johnson.
Role of PRL-3, a human muscle-specific tyrosine phosphatase, in angiotensin-II signaling.
Action of protein kinases and phosphatases contributes to myocardial hypertrophy. PRL-3, a protein tyrosine phosphatase, was identified in a cDNA library from an explanted human heart obtained from a patient with idiopathic cardiomyopathy. PRL-3 is expressed in heart and skeletal muscle, exhibiting approximately 76% identity to the ubiquitous tyrosine phosphatase PRL-1, which was reported to increase cell proliferation. PRL-3 was cloned into E. coli and purified using affinity chromatography. PRL-3 activity was determined using the substrate 6,8-difluoro-4-methylumbelliferyl phosphate, and was inhibited by vanadate and analogs. HEK293 cells expressing PRL-3 demonstrated increased growth rates versus nontransfected cells or cells transfected with the catalytically inactive C104S PRL-3 mutant. The tyrosine phosphatase inhibitor, potassium bisperoxo (bipyridine) oxovanadate V, normalizes the growth rate of PRL-3 expressing cells to that of parental HEK293 cells in a concentration-dependent manner. Using FLIPR analysis, parental HEK293 cells mobilize calcium when stimulated with angiotensin-II (AngII). However, calcium mobilization is inhibited in cells expressing wild-type PRL-3 when stimulated with AngII, while cells expressing the inactive mutant of PRL-3 mobilize calcium to the same extent as parental HEK293 cells. Western blots comparing PRL-3 transfected cells to parental HEK293 cells showed dephosphorylation of p130(cas) in response to AngII. These data suggest a role for PRL-3 in the modulation of intracellular calcium transients induced by AngII.
T cell proliferation and cytokine secretion to T cell epitopes of Asp f 2 in ABPA patients.
The pathogenesis of allergic bronchopulmonary aspergillosis (ABPA) involves specific cytokines secreted by lymphocytes in response to Aspergillus fumigatus (Af) allergens. To gain information about the lymphoproliferative response and cytokine production against a major Af allergen, Asp f 2, we studied Asp-f-2-specific T cell clones (TCCs) from ABPA patients. TCCs were stimulated with rAsp f 2, its deletion mutants, and synthetic peptides to identify the T cell epitope(s) and to understand cytokine production. PBMCs from four of five ABPA patients showed proliferation in response to Asp f 2. Three TCCs from one patient showed higher IL-5 secretion compared to IL-4 and IFN-gamma. Two TCCs from the second patient showed a mixed Th1/Th2 response, as evidenced by production of IL-4, IL-5, and IFN-gamma. An epitope from the N-terminal region of Asp f 2 induced only IL-5 secretion. High IL-5 secretion might explain the marked eosinophilia observed in ABPA patients.
Transdermal delivery of antisense oligonucleotides with microprojection patch (Macroflux) technology.
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An investigation of the validity and reliability of a food intake questionnaire.
AIMS: To evaluate the reliability and criterion validity of a food intake questionnaire (FIQ) designed for use in schoolchildren. METHODS: Study of reliability: 98 young people aged 13-14 years attending two schools in deprived areas of Liverpool completed the FIQ on three separate occasions over a 3-month period. VALIDITY STUDY: Ninety-six young people (aged 11-13 years) completed the FIQ and 2 weeks later completed a 3-day food diary (with interview). RESULTS: The FIQ gave consistent response on separate occasions over the 3-month reliability study period. Levels of agreement were consistent between survey combinations. Analysis of variance showed no differences in mean score for food groups between surveys. Pearson correlations for mean scores estimated by separate FIQ ranged from 0.42 for fibre food group to 0.76 for negative marker food group; the majority of the correlations were above 0.5. The data suggested the FIQ should be able to detect a change of +/-10% in eating habits. The validity study provided modest but significant Pearson correlations between energy intake, fat intake as a percentage of energy intake and sugars intake derived from 3-day diaries, and mean scores for the fatty, sugary and negative marker food group assessed by the FIQ. CONCLUSIONS: The results from both studies provide an indication of the FIQ's reliability, and suggest it has criterion validity for fatty and sugary and negative marker foods.
Painless electrodiagnostic current perception threshold and pain tolerance threshold values in CRPS subjects and healthy controls: a multicenter study.
The purpose of this study is to evaluate both painless and painful sensory transmission in patients with Complex Regional Pain Syndrome (CRPS) using the automated electrodiagnostic sensory Nerve Conduction Threshold (sNCT) test. This test generates reliable, painless Current Perception Threshold (CPT) and atraumatic Pain Tolerance Threshold (PTT) measures. Standardized CPT and PTT measures using constant alternating current sinusoid waveform stimulus at 3 different frequencies 5 Hz, 250 Hz, and 2 kHz (Neurometer CPT/C Neurotron, Inc. Baltimore, MD) were obtained from CRPS subjects at a distal phalange of the affected extremity and at an ipsilateral asymptomatic control site. Matched sites were tested on healthy subjects. Detection sensitivities for an abnormal PTT and CPT test were calculated based on specificity of 90% as determined from data obtained from healthy controls. A Spearman rank correlation was used to test for a significant association between presence of allodynia and an abnormal PTT or CPT at any frequency tested. Thirty-six CRPS subjects and 57 healthy controls were tested. The highest detection sensitivity of the PTT test from symptomatic test sites was 63% for the finger and 71% for the toe. PTT abnormalities were also detected, to a lesser degree, at the asymptomatic control site (41% finger control site, 16% toe control site). The highest CPT detection sensitivity at the symptomatic site was 37% for the finger site and 53% for the toe site. CPT abnormalities were also detected at the asymptomatic control site (29% finger control site, 37% toe control site). Eighty-six percent of the CRPS subjects had either a PTT or CPT abnormality at any frequency at the symptomatic site. There was a significant correlation between presence of allodynia and presence of an abnormal CPT and PTT, respectively (P < .01). The correlation coefficient was lower for CPT than for PTT, ie, 0.34 versus 0.6 for the finger and 0.48 versus 0.67 for the toe, respectively. In studied CRPS patients an abnormal PTT was detected with higher sensitivity than an abnormal CPT. Assessing PTT may become a useful electrodiagnostic quantitative sensory test for diagnosing and following the course of neuropathic pain conditions.
AcrySof acrylic intraocular lens implantation in children: clinical indications of biocompatibility.
PURPOSE: To assess the clinical biocompatibility of AcrySof (Alcon, Ft Worth, Tex) acrylic intraocular lenses (IOLs) in the highly reactive eyes of infants and children. METHODS: A database of 230 pediatric IOL implantations was queried to allow retrospective review of all eyes implanted with an AcrySof IOL. Eyes implanted with polymethyl methacrylate (PMMA) IOLs were also reviewed and were used as a historical comparison group. Follow-up examinations were conducted by the surgeon on postoperative day 1, day 7, week 4, and week 8 and every 3 months during the first year and every 6 months thereafter. The presence of synechiae, lens deposits, and posterior capsule opacification were noted in the record at each visit. Examination notes were photocopied, and data were extracted from each visit note and entered into a computerized database. RESULTS: One hundred and ten eyes had an AcrySof IOL at an average age of 60.4 months and had an average postoperative follow-up of 64.6 weeks. In comparison, 120 eyes had PMMA IOLs inserted at an average age of 71.9 months with an average postoperative follow-up of 136.9 weeks. IOL cell deposits were seen at the slit lamp in 7 of 110 (6.4%) AcrySof lenses as compared with 26 of 120 (21.75%) PMMA lenses (P =.002). Posterior synechiae were seen in 5 of 110 (4.5%) AcrySof lenses as compared with 23 of 120 (19.2%) PMMA lenses (P =.001). Twenty-two AcrySof-implanted eyes had an intact posterior capsule. Twenty-eight PMMA-implanted eyes had an intact posterior capsule. The YAG laser capsulotomy rate was similar in the 2 groups at 45.4% for AcrySof and 50% for PMMA (P =.973). The average time from surgery to YAG posterior capsulotomy was 18.6 months with an AcrySof lens and 18.3 months with a PMMA lens (P =.951; t test). A total of 60 patients (68%) implanted with AcrySof IOLs were able to cooperate for Snellen visual acuities. Of their 67 eyes, 48 (72%) had a 20/40 or better visual acuity at the last follow-up examination, and 63 eyes (94%) had a 20/100 or better visual acuity. Thirty-five eyes (52%) required amblyopia therapy, and patching continues as needed. CONCLUSIONS: The AcrySof IOL is representative of a new group of foldable IOLs made from flexible hydrophobic acrylic material. The AcrySof IOL appears clinically to be biocompatible when placed in the eyes of children despite the increased tissue reactivity known to occur in young patients.
Discharge planning for complex paediatric cases.
The aim of this study was to identify the functions performed by social workers specifically engaged in paediatric discharge planning by undertaking a detailed analysis of discharge planning practice in forty cases referred to a specialist discharge planning team, at the Royal Children's Hospital, Melborne. A second aim was to identify the characteristics that distinguished complex cases from more routine cases. Discharge planning activity focused on the family, community and the organisation, with most cases requiring activity in all three areas. More complex cases were characterised by amount of social work time spent on the case, length of stay and number of discharge planner functions performed, but not number of prior admissions.
Comparison of Roche MONITOR and Organon Teknika NucliSens assays to quantify human immunodeficiency virus type 1 RNA in cerebrospinal fluid.
We compared Roche MONITOR and Organon Teknika NucliSens assays for human immunodeficiency virus type 1 (HIV-1) RNA in cerebrospinal fluid (CSF). Results of 282 assays were highly correlated (r = 0.826), with MONITOR values being 0.29 +/- 0.4 log(10) copies/ml (mean +/- standard deviation) values. Both assays can reliably quantify HIV-1 RNA in CSF.
Adenosine, a metabolic trigger of the exercise pressor reflex in humans.
There is substantial evidence that adenosine activates muscle afferent nerve fibers leading to sympathetic stimulation, but the issue remains controversial. To further test this hypothesis, we used local injections of adenosine into the brachial artery while monitoring systemic muscle sympathetic nerve activity (MSNA) with peroneal microneurography. The increase in MSNA induced by 3 mg intrabrachial adenosine (106+/-32%) was abolished if forearm afferent traffic was interrupted by axillary ganglionic blockade (21+/-19%, n=5, P:<0.05). Furthermore, the increase in MSNA induced by intravenous adenosine was 3.7-fold lower and later (onset latency 20.9+/-4.8 seconds versus 8.5+/-1 seconds) than intrabrachial adenosine. Finally, we used forearm exercise (dynamic handgrip at 50% and 15% maximal voluntary contraction, MVC), with or without superimposed ischemia, to modulate interstitial levels of adenosine (estimated with microdialysis) while monitoring MSNA. Fifteen minutes of intense (50% MVC) and moderate (15% MVC) exercise increased adenosine dialysate concentrations from 0.31+/-0.1 to 1.24+/-0.4 micromol/L (528+/-292%) and from 0.1+/-0.02 to 0.419+/-0.16 micromol/L (303+/-99%), respectively (n=7, P:<0.01). MSNA increased 88+/-25% and 38+/-28%, respectively. Five minutes of moderate exercise increased adenosine from 0.095+/-0.02 to 0.25+/-0.12 micromol/L, and from 0.095+/-0.02 to 0.48+/-0.19 micromol/L when ischemia was superimposed on exercise (n=7, P:=0.01). The percent increase in MSNA induced by the various interventions correlated with the percent increase in dialysate adenosine levels (r=0.96). We conclude that adenosine activates muscle afferent nerves, triggering reflex sympathetic activation.
Drug dreams: a neuropsychoanalytic hypothesis.
Recent studies have shown that the ventral tegmental pathway stimulates both dreaming and drug craving. To investigate a possible clinical link between these two psychic phenomena, psychotherapy notes from the first six months of an addicted patient's treatment were reviewed, together with verbatim notes from the four years of psychoanalysis that followed. Of 240 dreams reported by the patient,58 had manifest content involving the seeking or using of drugs. There was no particular temporal or emotional thematic pattern to these "drug dreams,"which persisted through four and a half years of sobriety. Drug dreams are observable phenomena that reflect both the innate structure of the brain and neural changes produced by exposure to addictive drugs. In some addicted persons, exposure to drugs produces a fixed change in neurological functioning with which they must contend for years, possibly the rest of their lives. Drug craving meets Freud's defining characteristics for a drive: it is a constant pressure, originating from within the organism, to do work, and it constantly demands satisfaction. Because ego and libidinal drives share a common neural pathway, they should not be separated conceptually. Solms's finding (in press) that the activating systems for dreaming and for craving are identical, a finding based on observations of tumor- or stroke-provoked brain lesions, is confirmed by observation of the dreams of a patient whose brain changes were created by drug exposure. This study provides further evidence that the origin of the dream is a wish.
Mediators of lifestyle behavior change in Native Hawaiians: initial findings from the Native Hawaiian Diabetes Intervention Program.
OBJECTIVE: To examine the association of stage of change with diet and exercise behaviors in response to a lifestyle intervention for Native Hawaiians (NHs). RESEARCH DESIGN AND METHODS: A family ('ohana) support lifestyle intervention was compared with a standard intervention in NHs with or at risk for diabetes in two rural communities in Hawaii (n = 147). Stage of change, as a hypothesized mediator of behavior change, and dietary and exercise behaviors were measured at baseline and at 1 year postintervention. RESULTS: Stage of change was significantly associated with positive dietary and exercise behaviors. NHs receiving the 'ohana support (OS) intervention were more likely to advance from pre-action to action/maintenance for fat intake and physical activity than the group who received the standard intervention. Participants in the OS group who advanced from pre-action to action/maintenance showed more improvement in fat intake and physical activity than those in the standard group. CONCLUSIONS: These initial findings suggest that stage of change is an important factor in mediating lifestyle behavior changes in persons with or at risk for diabetes and merits further study among minority populations at high risk for diabetes.
Intraoperative microwave processing of bone margins during resection of head and neck cancer.
OBJECTIVE: To develop an accurate method for performing histopathologic analysis for a full cross-section of cortical bone within 2 to 3 hours. METHODS: Microwave technology was used to augment and to more rapidly perform fixation and decalcification of cortical bone. RESULTS: Using the methods described, slides suitable for histopathologic analyses regarding the presence or absence of malignant tumor were prepared in 2 to 3 hours and, in 10 patients studied, had a 100% correlation with slides prepared in 7 days using the standard decalcification technique. CONCLUSION: Microwave technology allows accurate assessment of a full cross-section of cortical bone regarding the presence or absence of malignant tumor within the time limits required for resection of a malignant head and neck tumor and reconstruction of the surgical defect.
Stress induces peroxisome biogenesis genes.
Peroxisomes are the cellular location of many antioxidants and are themselves significant producers of reactive oxygen species. In this report we demonstrate the induction of peroxisome biogenesis genes in both plant and animal cells by the universal stress signal molecule hydrogen peroxide. Using PEX1-LUC transgenic plants, rapid local and systemic induction of PEX1-luciferase could be demonstrated in vivo in response to physiological levels of hydrogen peroxide. PEX1-luciferase was also induced in response to wounding and to infection with an avirulent pathogen. We propose a model in which various stress situations that lead to the production of hydrogen peroxide can be ameliorated by elaboration of the peroxisome compartment to assist in restoration of the cellular redox balance.
Addiction: part II. Identification and management of the drug-seeking patient.
The medications most often implicated in prescription drug abuse are opioid analgesics, sedative-hypnotics and stimulants. Patients with acute or chronic pain, anxiety disorders and attention-deficit disorder are at increased risk of addiction comorbidity. It is important to ask patients about their substance-use history, including alcohol, illicit drugs and prescription drugs. Patients who abuse prescription drugs may exhibit certain patterns, such as escalating use, drug-seeking behavior and doctor shopping. A basic clinical survival skill in situations in which patients exert pressure on the physician to obtain a prescription drug is to say "no" and stick with it. Physicians who overprescribe can be characterized by the four "Ds"-dated, duped, dishonest and disabled. Maintaining a current knowledge base, documenting the decisions that guide the treatment process and seeking consultation are important risk-management strategies that improve clinical care and outcomes.
Addiction: Part I. Benzodiazepines--side effects, abuse risk and alternatives.
Benzodiazepines are widely prescribed for a variety of conditions, particularly anxiety and insomnia. They are relatively safe and, with overdose, rarely result in death. However, used chronically, benzodiazepines can be addicting. These agents are often taken in combination with other drugs of abuse by patients with addiction disorders. In such patients, alternatives to benzodiazepines may be preferable and may include antidepressants, anticonvulsants, buspirone, antihypertensive agents and the newer neuroleptic medications. Caution must be used when prescribing benzodiazepines to patients with a current or remote history of substance abuse.
DNA sequencing in a monolithic microchannel device.
We present 50 cm long microchannels in a monolithic device for high resolution, long read-length DNA sequencing. These devices were fabricated and bonded in borofloat glass using unconventional photolithography techniques with 48-188 independent, straight microchannels. The microchannel DNA separation was tested with POP-6 polymer and a DNA sequencing ladder separated at room temperature and 200 V/cm. Single-base resolution greater than 600 bases was achieved and the sequence base called to 640 bases with 98% accuracy. Under the same experimental conditions, the performance of the microchip was identical to a fused-silica capillary with similar cross-sectional area.
Establishing benchmarks for creation of a pro-forma economic model to evaluate filmless PACS operation.
The purpose of this study was to establish data points (benchmarks) to incorporate into a pro-forma cost analysis model, comparing film-based and filmless modes of operation. Prospective data were collected over a 6-year period at the Baltimore VA Medical Center (BVAMC) immediately before and after implementation of a hospital-wide PACS. These data were in turn compared with local and national VA centers during comparable time periods, to establish reference data between manual film-based (without PACS) and filmless operations (using PACS). Benchmarks utilized for the study fell into 2 broad categories: operational costs and revenues generated. Factors contributing to operational costs include space requirements, equipment, supplies, personnel, and maintenance. Factors contributing to revenues generated included examination volume, modality mix, and reimbursement rates. Collectively, these data points were incorporated into a pro-forma model that allows prospective PACS customers to compare total cost of ownership for film-based and filmless operations dependent on the unique variables of the respective institution.