Search PubMed⌕ Search

Biomedical subjects

D L Johnson

Publications and source records attributed to D L Johnson.

At least 181 records · Page 10Linked to original sources
PubMed1993

Apportioning the sources of lead in house dusts in the London borough of Richmond, England.

The sources of particulate lead in houses in the London Borough of Richmond, England have been investigated using automated scanning electron microscopy in conjunction with energy dispersive X-ray spectroscopy. Compositional and size information was collected on lead-bearing particles from density and size fractionated floor dusts from 16 residences of various ages. A classification scheme based on the analysis of different types of lead source particles was used to categorize the house dust particles as either auto exhaust, road dust, garden soil, paint, high temperature process emissions, lead of common origin or miscellaneous lead-bearing. Classification results based on both populations of particles and estimated particle volumes suggest that paint, road dust and garden soil are the major contributors of particulate lead to the Richmond households. The primary contributing source in the 64-1000-microm size range of the house dusts appears to be paint. In the 0-64-microm size fraction of the dusts paint, road dust and garden soil all make significant contributions. Variations in the contributions made by the major sources appear to be unrelated to the age of the homes.

Dust↗
PubMed1993

Urolithiasis in Dalmations: 275 cases (1981-1990).

From July 1, 1981 to December 31, 1990 the Urinary Stone Analysis Laboratory, School of Veterinary Medicine, University of California received 292 urinary calculi from 275 Dalmations (14 females, 14 episodes; 261 males, 278 episodes). The mean age of dogs at the time of the first episode of calculus formation was 4.5 years for males and 5.5 years for females. Bacteria were isolated from 22 of 49 calculi (45%). The bacteria were gram-positive with 2 exceptions; coagulase-positive staphylococci accounted for 62.5% of the isolates. Polarized light microscopy was used to determine the mineral content of the calculi. One hundred ninety three calculi were 100% urate; 78 calculi contained > or = 50% urate in 1 or more layers and were classified as mixed urate calculi; 7 calculi contained < 50% urate in all layers; and 14 calculi contained no urate. The secondary minerals most commonly encountered in mixed urate calculi were struvite (77%, 60 of 78 calculi), and oxalate (17%, 13 of 78 calculi). There were 65 struvite-containing calculi, 16 oxalate-containing calculi, 7 apatite-containing calculi, 5 silica-containing calculi, and 1 calculus specimen was composed of 100% cystine. The risk of forming urate-containing calculi was high in Dalmations, whereas the risk of forming calculi containing other minerals was consistently lower in Dalmations than in other breeds. X-ray diffraction and high pressure liquid chromatography were performed on all calculi from dogs known to have been given allopurinol (n = 19).(ABSTRACT TRUNCATED AT 250 WORDS)

Age Factors↗
PubMed1993

Vault ribonucleoprotein particles from rat and bullfrog contain a related small RNA that is transcribed by RNA polymerase III.

Vaults are large cytoplasmic ribonucleoprotein particles with a sedimentation value of about 150 S. These particles contain a unique small RNA (vault RNA (vRNA)). We have determined the sequence of the RNA associated with vaults purified from both rat and bullfrog. The rat vRNA is 141 bases in length, whereas the bullfrog vRNA is present as two highly related species of 89 and 94 bases. Despite the differences in length the predicted secondary structures of the three vRNAs are clearly related. All of the vRNAs contain sequences related to the internal promoter elements necessary for transcription by RNA polymerase III. The gene for the rat vRNA was isolated and sequenced from a rat genomic library, and its transcription by RNA polymerase III was verified using an in vitro transcription assay. The rat vRNA gene was efficiently transcribed in vitro, producing a single transcript of about 140 bases. Unlike most RNA polymerase III genes, the rat vRNA is present as a single copy gene and has a distinct tissue-specific expression pattern.

Animals↗
PubMed1993

Acalculous cholecystitis in bone marrow transplant patients.

BACKGROUND: Acalculous cholecystitis (ACC) is an uncommon disorder of the biliary tract, accounting for approximately 6% of acute cholecystitis cases. In this study, cholecystitis was seen in 8 of 770 bone marrow transplant recipients, with ACC occurring in five (63%). METHODS: Records of 592 allogenic and 150 autologous BMT patients were reviewed for risk factors associated with ACC. RESULTS: Only the number of blood transfusions administered and the use of total parenteral nutrition were associated with ACC development. ACC occurred in 4 of 42 (9%) allogeneic recipients who required exchange transfusion for ABO incompatibility. ACC developed in one autogolous recipient alongside venoocclusive disease of the liver. There was no association between ACC development and preparative regimen, cyclosporine usage, graft versus host disease, or cytomegalovirus infection. CONCLUSIONS: ACC occurs more frequently in patients after ABO incompatible BMT requiring exchange transfusion than in other transplant recipients.

ABO Blood-Group System↗
PubMed1993

Congenital mesoblastic nephroma: an immunohistochemical and lectin study.

Eight cases of congenital mesoblastic nephroma (CMN) were examined. Three CMNs were of the classical (typical) variant, two were cellular (atypical), and three showed a mixed pattern. A panel of nephron segment-specific tubular epithelial markers (the lectins Tetragonolobus purpureas, Phaseolus vulgaris erythroagglutinin, and Arachis hypogaea and antibodies to epithelial membrane antigen, cytokeratin, and Tamm-Horsfall protein) were used to differentiate epithelial structures within the tumor. Antibodies against vimentin, desmin, and muscle-specific actin were used as mesenchymal markers. A monoclonal antibody to the long (embryonic) form of polysialic acid (PSA) on the neural cell adhesion molecule was used as a putative renal oncodevelopmental marker. An antibody to proliferating cell nuclear antigen also was applied, which revealed increased proliferative rate in cellular CMNs. In addition to clearly entrapped native renal tubules, CMNs contain tubular structures with immature, dysplastic epithelium and occasional epithelial cell clusters embedded deep within the tumor. These immature tubules and clusters express distal nephron, including collecting duct markers and, occasionally, vimentin and PSA. We propose that these primitive tubules and epithelial structures may originate from the ureteric bud. An epithelial differentiation of the tumor cells also is possible. In one pure cellular CMN and two mixed CMNs the cellular component showed diffuse staining for PSA. The PSA (neural cell adhesion molecule) expression of the cellular component suggests that CMN may originate from the uninduced nephrogenic mesenchyme.

Child↗
PubMed1993

Relation of infant feeding practices, cigarette smoke exposure, and group child care to the onset and duration of otitis media with effusion in the first two years of life.

The relation of infant feeding practices, cigarette smoke exposure, and group child care to the onset and duration of otitis media with effusion (OME) was evaluated in a cohort of 698 healthy infants prospectively monitored by tympanometry in the home every 2 to 4 weeks until 2 years of age. Except for an experimental group of children who were offered early tube placement, the study children received conventional care from their personal physician or clinic. We used LISREL, a structural equation modeling procedure (computer software), to explore associations between environmental variables and OME onset and duration while controlling for interrelations among the variables. Supine feeding position and early initiation of group child care were associated with earlier onset of OME. Shorter duration of breast-feeding, increased packs of cigarettes smoked per day in the home, and increased hours per week in group child care were associated with an increase in the amount of time with OME during one or more of the age blocks studied (birth to 6, 6 to 12, 12 to 18, and 12 to 24 months). For a decrease in the amount of time with OME during the first 2 years of life, prolonged breast-feeding and upright feeding position should be encouraged, and cigarette smoke exposure should be minimized. Limiting early child care in large groups might also be advisable.

Breast Feeding↗
PubMed1993

The arthroscopic "impingement test" during anterior cruciate ligament reconstruction.

A primary goal of ACL reconstruction is to avoid graft impingement, which may lead to loss of motion and/or an increased incidence of instability. Although surgeons are cognizant of this potential problem, the intraoperative correction of graft impingement is technically demanding because the graft-notch relationship is obscured by the trochlea articulating with the tibial plateau during the final 10 degrees of extension. We present a simple impingement test that is performed before graft insertion and fixation to help avoid this potential pitfall.

Anterior Cruciate Ligament↗
PubMed1993

Does HOME add to the prediction of child intelligence over and above SES?

The most frequently used measure of the educational stimulation provided by the child's home environment is socioeconomic status (SES). Because SES is a global measure, researchers have developed measures that provide more detailed information. One of these is the Home Observation for Measurement of the Environment (HOME), (Caldwell & Bradley, 1984). Our research examined whether HOME adds to the predictability of child intelligence beyond that provided by SES. Subjects were 121 3-year-olds, Black and White, who were administered the fourth edition of the Stanford-Binet and the Peabody Picture Vocabulary Test-Revised. HOME and Hollingshead SES scores were obtained at age 2. HOME added to the predictability of intelligence over and above that provided by SES for the total group of children and for White children but not for Black children. The predictive utility of HOME also depended on the type of intelligence test being used.

Black or African American↗
PubMed1993

Use of alfentanil sedation anesthesia with the Dornier HM3 lithotripter.

Our results with the combination anesthetic technique of midazolam-alfentanil during elective outpatient extracorporeal shock wave lithotripsy on the Dornier HM3 (N = 79) were compared with those of epidural anesthesia in the same setting (N = 81). The mean anesthesia time and recovery room time were significantly shorter (72.85 v 113.58 minutes and 115.0 v 159.20 minutes, respectively) with the combination technique. No procedures in the alfentanil group had to be discontinued because of patient discomfort. Side effects with alfentanil were minimal, and oxygen saturation remained above 90% for all patients. Combination midazolam-alfentanil anesthesia is safe and allows the urologist to treat renal and ureteral calculi effectively and efficiently without using general or regional anesthesia.

Adult↗
PubMed1993

Variables affecting silicone-polymethyl methacrylate interfacial bond strengths.

PURPOSE: This study investigated the effects of various polymerization methods and of various types of silane coupling agents on the interfacial bond strengths of Molloplast-B and of two types of heat-processed polymethyl methacrylate (PMMA). MATERIALS AND METHODS: Standardized blocks of PMMA were processed and stored in 100% humidity for 14 days. Silicone of equal dimensions was flasked and processed with premixed and fresh-mixed silane coupling agents interposed. Processing utilized both a typical heated-water system and a dry-heat oven. Following recovery, the specimens were peel-tested at an angle of 180 degrees in an Instron machine. RESULTS: There was no significant difference between the test variables of Lucitone (Dentsply/York Division, York, PA) versus Lucitone 199 (Dentsply/York Division), nor with wet versus dry heat polymerization methods. However, the mean bond strengths for premixed silane improved slightly in a wet polymerization environment. Conversely, fresh-mixed silane's mean bond strength increased slightly with dry-heat polymerization. CONCLUSIONS: The bond strength between a methyl methacrylate denture base and a silicone soft liner varies only slightly when either Lucitone, Lucitone 199, or polymerization in a wet or dry environment is used. Under the conditions of this study, a fresh-mixed silane coupling agent produced a distinctly superior bond strength.

Acrylic Resins↗
PubMed1993

Adapting a dental surveyor to function in two planes.

Many bilateral distal extension removable partial dentures possess insufficient guidance to control their dislodgement. When such a situation is observed, the tips of retentive clasps must be located in both an occlusogingival and mesiodistal (away from the denture base area) undercut. The specific location can be identified with a dental surveyor that has been adapted to function in two planes. Details of the adaptation process and use of the surveyor are described.

Dental Clasps↗
PubMed1993

Traumatic atlanto-occipital dislocation in children.

During a 5-year period, 11 children were identified as having traumatic atlanto-occipital dislocation injury on the basis of clinical and radiographic findings. Radiographic criteria including the distance between the tip of the dens and the basion (DB distance), the BC/OA ratio (ratio of the distance between the basion and the posterior arch of C-1 divided by the distance between the opisthion and the anterior arch of C-1; normal ratio, < 1), and the width of the atlanto-occipital joint (normal width, < or = 5 mm) were correlated with clinical presentation and outcome. Normal pediatric values for DB distance were reviewed in a series of 110 lateral cervical spine radiographs. The normal DB distance was 8.3 mm +/- 4.2 (mean +/- 2 standard deviations). All 11 children had DB distances greater than 1.4 cm (mean, 1.7 cm). The BC/OA ratio was greater than 1 in only six patients. Of the 11 children, six died with severe neurologic deficits and five survived with minimal or no neurologic sequela. Without the clinical presentation variable, widened DB distance may be the first abnormality identified to suggest atlanto-occipital injury.

Atlanto-Occipital Joint↗
PubMed1993

Assessment of three-year-olds with the Stanford-Binet Fourth Edition.

The Stanford-Binet, Fourth Edition was normed for children 30 months of age and older, but its usefulness with young children (e.g., 36 months) has received little attention. This study of 121 three-year-old children examined possible administration problems, provided correlations with three environmental measures, and compared scores with those of the Peabody Picture Vocabulary Test--Revised. Problems of administration did arise on some subtests, correlations with environmental measures were moderate, and scores on the Stanford-Binet IV and PPVT-R were moderately correlated. The Stanford-Binet IV is a useful test in assessment of a broad range of intellectual abilities.

Child, Preschool↗
PubMed1993

Intractable hiccups: treatment by microvascular decompression of the vagus nerve. Case Report.

Idiopathic hiccups are usually managed with pharyngeal stimulation or a plethora of pharmacological agents. Hiccups that persist and prove intractable to these medical measures are treated by crush or ablation of the phrenic nerve, which denervates the major respiratory muscle. This is the first reported case of nondestructive microvascular decompression of the vagus nerve for the treatment of intractable idiopathic hiccups. The success of microvascular decompression has been documented with other conditions, such as trigeminal neuralgia and hemifacial spasm, that are characterized by hyperactive dysfunctional neurovascular contact. The vagus nerve was separated from the posterior inferior cerebellar artery by inserting a Teflon pledget between the nerve and vessel which eliminated the neurovascular contact. One year after the initial surgery, the hiccups recurred. The Teflon pledget had fallen out of place and the nerve was once again in contact with the artery. Once the contact was eliminated by wrapping the artery with a tuft of Teflon, the hiccups stopped. The patient has remained free of hiccups for 3 years. It is concluded that patients with intractable idiopathic hiccups who fail medical therapy should be considered for microvascular decompression of the vagus nerve.

Adolescent↗
PubMed1993

Posterior cruciate ligament injuries.

Posterior cruciate ligament (PCL) injuries are more common than has been previously reported. Recent clinical and basic science studies have helped define the important functional anatomy and biomechanics of this "forgotten" ligament and have raised questions regarding the reported benign natural history of isolated tears of the PCL. While recent technical advancements in the application of magnetic resonance imaging to knee ligament injuries may assist in identifying PCL tears, the posterior drawer test remains the "gold standard" for diagnosis. Numerous treatment options have been proposed, but anatomical reconstructions have yielded consistently good clinical results. A review of our current knowledge of the basic science and clinical studies on the posterior cruciate ligament is presented to stimulate further interest and research in this exciting area.

Acute Disease↗