PubMed Health⌕ Search

Biomedical subjects

K Johnson

Publications and source records attributed to K Johnson.

At least 19 recordsLinked to original sources
PubMed2006

Watershed nitrogen and mercury geochemical fluxes integrate landscape factors in long-term research watersheds at Acadia National Park, Maine, USA.

This paper is an overview of this special issue devoted to watershed research in Acadia National Park (Acadia NP). The papers address components of an integrated research program on two upland watersheds at Acadia NP, USA (44 degrees 20' N latitude; 68 degrees 15' E longitude). These watersheds were instrumented in 1998 to provide a long-term foundation for regional ecological and watershed research. The research was initiated as part of EPA/NPS PRIMENet (Park Research and Intensive Monitoring of Ecosystems Network), a system of UV-monitoring stations and long-term watershed research sites located in US national parks. The initial goals at Acadia NP were to address research questions about mercury, acid rain, and nitrogen saturation developed from prior research. The project design was based on natural differences in forests and soils induced by an intense wildfire in one watershed in 1947. There is no evidence of fire in the reference watershed for several hundred years. We are testing hypotheses about controls on surface water chemistry, and bioavailability of contaminants in the contrasting watersheds. The unburned 47-ha Hadlock Brook watershed is 70% spruce-fir mature conifer forest. In contrast, burned 32-ha Cadillac Brook watershed, 4 km northeast of the Hadlock watershed, is 20% regenerating mixed northern hardwoods and 60% shrub/rocky balds. Differences in atmospheric deposition are controlled primarily by forest stand composition and age. The watersheds are gauged and have water chemistry stations at 122 m (Cadillac) and 137 m (Hadlock); watershed maximum elevations are 468 and 380 m, respectively. The stream water chemistry patterns reflect, in part, the legacy of the intense fire, which, in turn, controls differences in forest vegetation and soil characteristics. These factors result in higher nitrogen and mercury flux from the unburned watershed, reflecting differences in atmospheric deposition, contrasting ecosystem pools of nitrogen and mercury, and inferred differences in internal cycling and bioavailabilty.

Acid Rain↗
PubMed2006

Clinical assessment and core outcome variables are poor predictors of hip arthritis diagnosed by MRI in juvenile idiopathic arthritis.

OBJECTIVES: To compare the diagnostic performance of clinical assessment against magnetic resonance imaging (MRI) diagnosed hip arthritis in a juvenile idiopathic arthritis (JIA) population. To determine the clinical and serological predictors of MRI diagnosed hip arthritis. METHODS: A total of 34 JIA patients with established disease (mean disease duration 6.3 yrs) had their hip MRIs scored for features of active hip arthritis and hip damage. Results were compared with clinical variables (disease subtype, history of hip pain, core outcome variables (COV)) and the clinician's assessment of active hip arthritis. RESULTS: MRI features of active hip arthritis were found in 45 hips (70%) and hip damage in 36 hips (56%). Clinical assessment had fair agreement with MRI scoring of active arthritis in patients with disease duration <4 yrs (kappa score 0.38, P = 0.045). Clinical assessment had a sensitivity of 25.7% and specificity of 91% for detecting MRI diagnosed arthritis. Of the core outcome variables only erythrocyte sedimentation rate predicted inflammation detected on MRI (r = 0.44, P = 0.014). CONCLUSIONS: The association between the clinician's assessment, core outcome variables and MRI findings in this study was limited. This indicates that clinical and laboratory findings are inadequate diagnostic tools for the assessment of hip arthritis when compared with MRI as the gold standard.

Adolescent↗
PubMed2006

Nephrotic syndrome associated with chronic graft-versus-host disease after allogeneic hematopoietic stem cell transplantation.

Chronic graft-versus-host disease (cGVHD) is the most common late complication of allogeneic hematopoietic cell transplantation (HCT) causing significant morbidity and mortality. The kidneys are not considered a target organ for cGVHD in humans, although animal models show renal damage. Renal involvement in patients with cGVHD, presenting as nephrotic syndrome (NS), has rarely been reported in patients who received allogeneic transplantation. Herein we describe, by far, the largest series of nine patients with NS associated with cGVHD, including two patients who received a reduced-intensity regimen. Pathological features of membranous nephropathy were the most common finding on renal biopsy. The clinical course of the NS was temporally associated with the classical features of cGVHD in all but one of the nine cases. The clinicopathologic features of NS in our series as well as reports in the literature demonstrate an immunopathologic process typical of antibody-mediated damage consistent with cGVHD. Treatment directed against antibody-mediated damage, such as anti-B-cell antibody may play an important role in ameliorating NS associated with cGVHD.

Adult↗
PubMed2006

Elastic scattering spectroscopy accurately detects high grade dysplasia and cancer in Barrett's oesophagus.

BACKGROUND AND AIMS: Endoscopic surveillance of Barrett's oesophagus currently relies on multiple random biopsies. This approach is time consuming, has a poor diagnostic yield, and significant interobserver variability. Elastic scattering spectroscopy is a real time in vivo optical technique which detects changes in the physical properties of cells. The aim of this study was to assess the potential for elastic scattering to detect high grade dysplasia or cancer within Barrett's oesophagus. METHODS: Elastic scattering spectroscopy measurements collected in vivo were matched with histological specimens taken from identical sites within Barrett's oesophagus. All biopsies were reviewed by three gastrointestinal pathologists and defined as either "low risk" (non-dysplastic or low grade dysplasia) or "high risk" (high grade dysplasia or cancer). Two different statistical approaches (leave one out and block validation) were used to validate the model. RESULTS: A total of 181 matched biopsy sites from 81 patients, where histopathological consensus was reached, were analysed. There was good pathologist agreement in differentiating high grade dysplasia and cancer from other pathology (kappa = 0.72). Elastic scattering spectroscopy detected high risk sites with 92% sensitivity and 60% specificity and differentiated high risk sites from inflammation with a sensitivity and specificity of 79%. If used to target biopsies during endoscopy, the number of low risk biopsies taken would decrease by 60% with minimal loss of accuracy. A negative spectroscopy result would exclude high grade dysplasia or cancer with an accuracy of >99.5%. CONCLUSIONS: These preliminary results show that elastic scattering spectroscopy has the potential to target conventional biopsies in Barrett's surveillance saving significant endoscopist and pathologist time with consequent financial savings. This technique now requires validation in prospective studies.

Adenocarcinoma↗
PubMed2006

A 3' cis-regulatory region controls wingless expression in the Drosophila eye and leg primordia.

The precise regulation of wingless (wg) expression in the Drosophila eye disc is key to control the anteroposterior and dorsoventral patterning of this disc. Here, we identify an eye disc-specific wg cis-regulatory element that functions as a regulatory rheostat. Pannier (Pnr), a transcription factor previously proposed to act as an upstream activator of wg, is sufficient to activate the eye disc enhancer but required for wg expression only in the peripodial epithelium of the disc. We propose that this regulation of wg by Pnr appeared associated to the development of the peripodial epithelium in higher dipterans and was added to an existing mechanism regulating the deployment of wingless in the dorsal region of the eye primordium. In addition, our analysis identifies a separate ventral disc enhancer that lies adjacent to the eye-specific one, and thus altogether, they define a 1-kb genomic region where disc-specific enhancers of the wg gene are located.

3' Untranslated Regions↗
PubMed2006

Highly constrained backprojection for time-resolved MRI.

Recent work in k-t BLAST and undersampled projection angiography has emphasized the value of using training data sets obtained during the acquisition of a series of images. These techniques have used iterative algorithms guided by the training set information to reconstruct time frames sampled at well below the Nyquist limit. We present here a simple non-iterative unfiltered backprojection algorithm that incorporates the idea of a composite image consisting of portions or all of the acquired data to constrain the backprojection process. This significantly reduces streak artifacts and increases the overall SNR, permitting decreased numbers of projections to be used when acquiring each image in the image time series. For undersampled 2D projection imaging applications, such as cine phase contrast (PC) angiography, our results suggest that the angular undersampling factor, relative to Nyquist requirements, can be increased from the present factor of 4 to about 100 while increasing SNR per individual time frame. Results are presented for a contrast-enhanced PR HYPR TRICKS acquisition in a volunteer using an angular undersampling factor of 75 and a TRICKS temporal undersampling factor of 3 for an overall undersampling factor of 225.

Algorithms↗
PubMed2005

Varying Ti-6Al-4V surface roughness induces different early morphologic and molecular responses in MG63 osteoblast-like cells.

Osteoblast response to Ti implants depends not only on the chemistry of the implant but also on the physical properties of the implant surface, such as microtopography and roughness. This study was undertaken to examine early changes in cell morphology and gene expression during the early phase of osteoblast interaction with titanium alloy (Ti-6Al-4V) surfaces of two different roughnesses. MG63 osteoblast-like cells were cultured for 2, 6, 24, and 72 h on smooth (Ra=0.18+/-0.03 microm) and rough (Ra=2.95+/-0.23 microm) Ti-6Al-4V surfaces. Changes in cell proliferation were assessed by measuring cell number after 72 h in culture. Morphological characteristics were observed by scanning electron microscopy after 2, 6, and 24 h of culture. Changes in gene expression for extracellular signal-regulated kinase 2 (Erk2), type I collagen (alpha2[I] collagen), phospholipase C-gamma2 (Plc-gamma2), and beta-actin were measured by RT-PCR after 6 and 24 h in culture. Cell number was significantly higher on the smooth surface. In scanning electron micrographs, cells on smooth Ti-6Al-4V were spherical and raised up from the surface after 2 h in culture. In contrast, cells on the rough surface adopted an irregular, elongated shape that spanned across pits in the surface. At 24 h, cells on the smooth surface had flattened, become elongate, and covered the surface. In contrast, cells on the rough surface appeared more differentiated in shape and the margins of the cells were irregular, with many processes extending out, following the contour of the surface. Of the genes examined, only Erk2 and beta-actin showed a change in expression with surface roughness. Both genes were upregulated (p<0.05) on the rough surface at 6 h. These results indicate that Ti-6Al-4V surface roughness affects osteoblast proliferation, morphology, and gene expression, and that these effects can be measured after periods as short as 2-6 h.

Alloys↗
PubMed2005

Preoperative colonoscopy decreases the need for laparoscopic management of colonic polyps.

PURPOSE: Patients are commonly referred to surgeons for surgical resection of polyps that cannot be excised colonoscopically. Repeating the colonoscopy may be met with resistance by both the patient and the referring endoscopist. However, there are two distinct benefits. First, if the lesion was not marked, tattooing facilitates laparoscopic resection. Second, and more importantly, many of these polyps can be removed endoscopically by an experienced colorectal surgeon, avoiding unnecessary colon resection. Over a period of five years, we have reviewed preoperative colonoscopy in patients who were referred for surgical treatment of benign polyps. METHODS: From January 1999 through September 2003 all patients referred for surgical resection of a benign polyp were consecutively entered into a database by a single group of colorectal surgeons. All patients underwent preoperative colonoscopy on the day before the planned colon resection. Patient charts were reviewed, and demographics were recorded. The referral and preoperative colonoscopy reports and all pathology results were reviewed to record the polyp size, location, histology, and subsequent treatment. RESULTS: Altogether, 71 patients were included in this study. The average size of the polyps was 24 mm (range, 10-60 mm). The location of the polyp as determined by preoperative colonoscopy differed from the location noted on referral colonoscopy in nine patients (13 percent). Surgery was canceled in 23 patients (32 percent), primarily because of complete polypectomy at preoperative colonoscopy. Of the 48 who underwent surgery, 23 (47 percent) had a colonic tattoo placed, at the discretion of the surgeon. Lesions clearly located in the cecum were not tattooed routinely. Of the 48 patients who underwent surgery, 45 (94 percent) underwent laparoscopic colon resection. CONCLUSIONS: We concluded that patients referred for surgical resection of a polyp should undergo repeat colonoscopy preoperatively, given that in our study one-third of patients were spared unnecessary colectomy. In addition, repeat endoscopy by the operating surgeon offers an opportunity to confirm the location of the lesion and place a colonic tattoo to facilitate laparoscopic resection.

Aged↗
PubMed2005

Accidental head injuries in children under 5 years of age.

AIM: To evaluate the type and nature of head injuries sustained by children under the age of 5 years who present to a busy accident and emergency (A&E) department following an accidental fall. MATERIALS AND METHODS: This study included all children under the age of 5 years, who over an 8-month period were referred to our A&E Department with head injury following an accidental fall. Data were collected regarding the height of the fall, whether or not stairs were involved, the type of surface that the child landed on and the height of the child. This was correlated with any soft-tissue injury or skull fracture. RESULTS: A total of 72 children (aged 4 months to 4.75 years) fulfilled all the criteria for an accidental fall. The heights of the falls ranged from less than 50 cm to over 3 m, with the majority below 1 m. Of the falls, 49 were onto a hard surface and 23 were onto a soft surface. Of the 72 children, 52 had visible evidence of head injury, 35 (71%) of 49 being the result of falls onto hard surfaces and 17 (74%) of 23 onto soft (carpeted) surfaces. There was no significant difference in the type of surface that resulted in a visible head injury. A visible head injury was seen in all children who fell from a height of over 1.5 m and in 95% of children who fell over 1 m. Of the 72 children, 32 (44%) had skull radiographs performed in accordance with established guidelines and 4 (12.5%) were identified as having a fracture. Of the 3 linear parietal fractures 2 were inflicted by falls of just over 1 m (from a work surface) and 1 by a fall of 80 to 90 cm onto the hard-edged surface of a stone fire surround. The 4th was a fracture of the base of skull following a fall from more than 3 m (from a first-storey window). CONCLUSIONS: In the vast majority of domestic accidents children do not suffer significant harm. Skull fractures are rare and probably occur in less than 5% of cases. To cause a skull fracture the fall needs to be from over 1 m or, if from a lesser height, then a small-area impact point should be considered an integral component of the injury.

Accidental Falls↗
PubMed2005

Detection of Renibacterium salmoninarum in chinook salmon, Oncorhynchus tshawytscha (Walbaum), using quantitative PCR.

A quantitative polymerase chain reaction (QPCR) assay has been developed to detect varying levels of Renibacterium salmoninarum, the causative agent of bacterial kidney disease. This assay allows for the direct enumeration of bacterial DNA or RNA copy number within tissues and body fluids. The assay can be applied non-lethally and can be used to determine whether R. salmoninarum is transcriptionally active. The presence of R. salmoninarum in kidney tissues from 430 chinook salmon collected from five Idaho Fish and Game operated hatcheries was initially evaluated using the widely employed enzyme-linked immunosorbent assay (ELISA) with two sets of Kirkegaard and Perry Laboratories polyclonal antibodies, 'mother batches' 1 and 2. The same tissue samples were then analysed using the novel QPCR assay and the results compared. At moderate to high levels of infection [optical density (OD > 0.5)], ELISA values and estimated DNA copy number were highly correlated (r(2) > 0.80), although correlation to specific antibody batches varied. However, lower ELISA values (OD < 0.5) observed with either antibody batch did not correlate well with the QPCR assay (R(2) <or= 0.43). Negative controls, run concurrently with the PCR assay, did not indicate extraneous DNA contamination in the PCR samples.

Actinomycetales Infections↗
PubMed2005

Correlation of membranous glomerular ultrastructural changes with disease severity and outcome in lupus patients initiating cyclophosphamide therapy.

The aim of this study was to assess the utility applying an electron microscopy (EM) scoring system used in idiopathic membranous nephritis based on the location of subepithelial and/or intramembranous electron dense deposits in interpretation of renal biopsies from patients with lupus nephritis. We selected patients with electron dense deposits traditionally associated with membranous changes on EM from 84 patients treated with bolus cyclophosphamide, with five years follow-up. An EM scoring system designed for idiopathic membranous nephritis was applied (stages I or II, mild changes; stages III or IV, advanced changes). Twenty-seven out of 84 had membranous changes by light microscopy, of whom 22 had satisfactory tissue for EM membranous analysis. Eleven out of 22 had mild EM changes (EM stage I or II); 11 had advanced disease (EM stage III). Advanced EM stage was associated with a higher serum creatinine at entry when tests were adjusted for WHO class (2.62 +/- 0.6 versus 1.31 +/- 0.28 mg/dL, P < 0.022 by ANOVA), and EM stage was independent of NIH activity or chronicity indexes or disease duration. After five years, adverse outcomes (death or dialysis) were seen in one of the 11 patients with EM stages I-II versus five of the 11 EM stage III patients (P < 0.07). Advanced membranous type electron dense deposition in lupus as assessed by EM was associated with worse renal function in patients with comparable WHO classification and NIH activity and chronicity indexes. In this group of lupus patients initiating cyclophosphamide for severe nephritis, EM stage provided important additional information regarding the extent of renal injury.

Basement Membrane↗
PubMed2005

Education in end-of-life care: bridging disciplinary and institutional boundaries.

This paper describes the development of an interdisciplinary, interinstitutional seminar in palliative care for South Dakota students in medicine, nursing, pharmacy, chaplaincy, and social work. Student outcomes from six seminars conducted during 2001-2004 are reported, and recommendations for future educational efforts are outlined.

Curriculum↗
PubMed2004

Mapping Ds insertions in barley using a sequence-based approach.

A transposon tagging system, based upon maize Ac/Ds elements, was developed in barley (Hordeum vulgaresubsp. vulgare). The long-term objective of this project is to identify a set of lines with Ds insertions dispersed throughout the genome as a comprehensive tool for gene discovery and reverse genetics. AcTPase and Ds-bar elements were introduced into immature embryos of Golden Promise by biolistic transformation. Subsequent transposition and segregation of Ds away from AcTPase and the original site of integration resulted in new lines, each containing a stabilized Ds element in a new location. The sequence of the genomic DNA flanking the Ds elements was obtained by inverse PCR and TAIL-PCR. Using a sequence-based mapping strategy, we determined the genome locations of the Ds insertions in 19 independent lines using primarily restriction digest-based assays of PCR-amplified single nucleotide polymorphisms and PCR-based assays of insertions or deletions. The principal strategy was to identify and map sequence polymorphisms in the regions corresponding to the flanking DNA using the Oregon Wolfe Barley mapping population. The mapping results obtained by the sequence-based approach were confirmed by RFLP analyses in four of the lines. In addition, cloned DNA sequences corresponding to the flanking DNA were used to assign map locations to Morex-derived genomic BAC library inserts, thus integrating genetic and physical maps of barley. BLAST search results indicate that the majority of the transposed Ds elements are found within predicted or known coding sequences. Transposon tagging in barley using Ac/Ds thus promises to provide a useful tool for studies on the functional genomics of the Triticeae.

Base Sequence↗
PubMed2004

Calcification in calcium pyrophosphate dihydrate (CPPD) crystalline deposits in the knee: anatomic, radiographic, MR imaging, and histologic study in cadavers.

OBJECTIVE: To demonstrate and determine the frequency and location of calcification within cadaveric knees with or without calcification typical of calcium pyrophosphate dihydrate (CPPD), utilizing histologic, radiographic and MR imaging techniques. DESIGN AND PATIENTS: Ten cadaveric knees of elderly individuals that demonstrated no radiographic evidence of prior surgery or trauma were studied with MR imaging and subsequently sectioned in planes corresponding to those obtained with MR imaging. The slices were imaged with high-resolution radiography. Two musculoskeletal radiologists correlated the anatomic, MR and radiographic findings. Three of the knees, which did not demonstrate calcifications, were utilized as controls. Histologic sections were obtained from four knees that contained calcifications and from the three controls, and analyzed with special histologic stains that demonstrate phosphorus and calcium. RESULTS: Radiographic imaging and histologic analysis demonstrated widespread CPPD crystal deposition in four of the 10 knee specimens (40%). MR imaging demonstrated some calcifications only within the articular cartilage of the femoral condyles in three of the four (75%) specimens that had CPPD deposits. In all four specimens radiographs and histologic analysis were more sensitive than MR imaging. Histologic analysis demonstrated no evidence of CPPD crystals in the control specimens. CONCLUSION: MR imaging is insensitive to the presence of CPPD deposits in the knee, even when such deposits are widespread. Our study suggests that the sensitivity of MR imaging was significantly better in detecting CPPD deposits in the hyaline cartilage of the femoral condyles when compared with other internal structures, even when such structures contained a higher amount of calcification.

Aged↗
PubMed2004

Reducing unnecessary skull radiographs in children: a multidisciplinary audit.

AIM: To review guidelines on the indications for skull radiographs with a view to improving compliance and reducing unnecessary irradiation of children. METHODS: Three audits on the indications, compliance and effect on practice of differing sets of guidelines for skull radiographs following paediatric head trauma were performed. After each audit, alterations in clinical practice with modifications of the guidelines were implemented. The effect of these changes on radiological practice and patient care were recorded. Audits were performed for 3 months (February-April) in 1999, 2001 and 2003. RESULTS: The number of children with head injuries presenting was unchanged. The number of skull radiographs performed fell from 146 in 1999 to 95 in 2001 and 50 in 2003. Compliance with hospital guidelines increased from 85% in 1999 to 100% in 2003. No neurosurgical problems were missed. CONCLUSION: The implementation of guidelines that are acceptable to all specialties will improve compliance and reduce unnecessary radiographs being performed. The involvement of the radiography staff will help maintain compliance. The training of junior staff and maintaining good communication with involved departments will improve patient care.

Child↗
PubMed2004

MRI of the marrow in the paediatric skeleton.

Magnetic resonance imaging (MRI) has greatly advanced evaluation of marrow diseases of the paediatric skeleton. As with many other aspects of paediatric radiology it is important to recognize the normal variations in the appearance of the marrow that occur in the growing child. These normal variations need to be differentiated from diseases and conditions that affect the marrow. This review describes the normal changes that occur in children with age, and the appearances of the pathological changes seen in infection, infiltration, haematological disorders, transplantation and radiation therapy.

Bone Marrow Diseases↗
PubMed2004

Upregulated ank expression in osteoarthritis can promote both chondrocyte MMP-13 expression and calcification via chondrocyte extracellular PPi excess.

OBJECTIVE: In idiopathic chondrocalcinosis and in osteoarthritis (OA), increased extracellular PP(i) (ecPP(i)) promotes calcification. In chromosome 5p-associated familial chondrocalcinotic degenerative arthropathy, certain mutations in the membrane protein ANK may chronically raise ecPP(i) via enhanced PP(i) channeling. Therefore, we assessed if dysregulated wild-type ANK expression could contribute to pathogenesis of idiopathic degenerative arthropathy through elevated ecPP(i). DESIGN: Using cells with genetic alterations in expression of ANK and the PP(i)-generating nucleotide pyrophosphatase phosphodiestrase (NPP) PC-1, we examined how increased ANK expression elevates ecPPI, testing for codependent effects with PC-1. We also evaluated the effects of ANK expression on chondrocyte growth, matrix synthesis, and MMP-13 expression and we immunohistochemically examined ANK expression in situ in human knee OA cartilages. RESULTS: Using cells expressing defective ANK, as well as PC-1 knockout cells, we demonstrated that ANK required PC-1 (and vice versa) to raise ecPP(i) and that the major ecPP(i) regulator TGFbeta required both ANK and PC-1 to elevate ecPP(i). Upregulation of wild-type ANK by transfection in normal chondrocytes not only raised ecPP(i) 5-fold to approximately 100nM but also directly stimulated matrix calcification and inhibited collagen and sulfated proteoglycans synthesis. In addition, upregulated ANK induced chondrocyte MMP-13, an effect that also was stimulated within 2h by treatment of chondrocytes with 100nM PP(i) alone. Finally, ANK expression was upregulated in situ in human knee OA cartilages. CONCLUSION: Elevation of ecPP(i) by ANK critically requires the fraction of cellular PP(i) generated by PC-1. The upregulation of ANK expression in OA cartilage and the capacity of increased ANK expression to induce MMP-13 and to promote matrix loss suggest that increased ANK expression and ecPP(i) exert noxious effects in degenerative arthropathies beyond stimulation of calcification.

Animals↗