Precipitation casting of drug-loaded microporous PCL matrices: Incorporation of progesterone by co-dissolution

Microporous, poly(epsilon-caprolactone) (PCL) matrices were loaded with progesterone by precipitation casting using co-solutions of PCL and progesterone in acetone. Progesterone loadings up to 32% w/w were readily achieved by increasing the drug content of the starting PCL solution. The kinetics of steroid release in PBS at 37 degrees C over 10 days could be described effectively by a diffusional release model although the Korsmeyer-Peppas model indicated the involvement of multiple release phenomena. The diffusion rate constant (D) increased from 8 to 24 microg/mg matrix/day0.5 as the drug loading increased from 3.6 to 12.4% w/w. A total cumulative release of 75%-95% indicates the high efficiency of steroid delivery. Increasing the matrix density from 0.22 to 0.39 g/cm3, by increasing the starting PCL solution concentration, was less effective in changing drug release kinetics. Retention of anti-proliferative activity of released steroid was confirmed using cultures of breast cancer epithelial (MCF-7) cells. Progesterone released from PCL matrices into PBS at 37 degrees C over 14 days retarded the growth of MCF-7 cells by a factor of at least 3.5 compared with progesterone-free controls. These findings recommend further investigation of precipitation-cast PCL matrices for delivery of bioactive molecules such as anti-proliferative agents from implanted, inserted or topical devices.

A co-cultured skin model based on cell support membranes

Tissue engineering of skin based on collagen:PCL biocomposites using a designed co-culture system is reported. The collagen:PCL biocomposites having collagen:PCL (w/w) ratios of 1:4, 1:8, and 1:20 have been proven to be biocompatible materials to support both adult normal human epidermal Keratinocyte (NHEK) and mouse 3T3 fibroblast growth in cell culture, respectively, by Dai, Coombes, et al. in 2004. Films of collagen:PCL biocomposites were prepared using non-crosslinking method by impregnation of lyophilized collagen mats with PCL/dichloromethane solutions followed by solvent evaporation. To mimic the dermal/epidermal structure of skin, the 1:20 collagen:PCL biocomposites were selected for a feasibility study of a designed co-culture technique that would subsequently be used for preparing fibroblast/biocomposite/keratinocyte skin models. A 55.3% increase in cell number was measured in the designed co-culture system when fibroblasts were seeded on both sides of a biocomposite film compared with cell culture on one surface of the biocomposite in the feasibility study. The co-culture of human keratinocytes and 3T3 fibroblasts on each side of the membrane was therefore studied using the same co-culture system by growing keratinocytes on the top surface of membrane for 3 days and 3T3 fibroblasts underneath the membrane for 6 days. Scanning electron microscopy (SEM) and immunohistochemistry assay revealed good cell attachment and proliferation of both human keratinocytes and 3T3 fibroblasts with these two types of cells isolated well on each side of the membrane. Using a modified co-culture technique, a co-cultured skin model presenting a confluent epidermal sheet on one side of the biocomposite film and fibroblasts populated on the other side of the film was developed successfully in co-culture system for 28 days under investigations by SEM and immunohistochemistry assay. Thus, the design of a co-culture system based on 1:20 (w/w) collagen:PCL biocomposite membranes for preparation of a bi-layered skin model with differentiated epidermal sheet was proven in principle. The approach to skin modeling reported here may find application in tissue engineering and screening of new pharmaceuticals.

Composite cell support membranes based on collagen and polycaprolactone for tissue engineering of skin

The preparation and characterisation of collagen:PCL composites for manufacture of tissue engineered skin substitutes and models are reported. Films having collagen:PCL (w/w) ratios of 1:4, 1:8 and 1:20 were prepared by impregnation of lyophilised collagen mats by PCL solutions followed by solvent evaporation. In vitro assays of collagen release and residual collagen content revealed an expected inverse relationship between the collagen release rate and the content of synthetic polymer in the composite that may be exploited for controlled presentation and release of biopharmaceuticals such as growth factors. DSC analysis revealed the characteristic melting point of PCL at around 60 degrees C and a tendency for the collagen component, at high loading, to impede crystallinity development within the PCL phase. The preparation of fibroblast/composite constructs was investigated using cell culture as a first stage in mimicking the dermal/epidermal structure of skin. Fibroblasts were found to attach and proliferate on all the composites investigated reaching a maximum of 2 x 10(5)/cm(2) on 1:20 collagen:PCL materials at day 8 with cell numbers declining thereafter. Keratinocyte growth rates were similar on all types of collagen:PCL materials investigated reaching a maximum of 6.6 x 10(4)/cm(2) at day 6. The results revealed that composite films of collagen and PCL are favourable substrates for growth of fibroblasts and keratinocytes and may find utility for skin repair.

Effects of paramyxoviral infection on airway epithelial cell Foxj1 expression, ciliogenesis, and mucociliary function

To elucidate molecular mechanisms underlying the association between respiratory viral infection and predisposition to subsequent bacterial infection, we used in vivo and in vitro models and human samples to characterize respiratory virus-induced changes in airway epithelial cell morphology, gene expression, and mucociliary function. Mouse paramyxoviral bronchitis resulted in airway epithelial cell infection and a distinct pattern of epithelial cell morphology changes and altered expression of the differentiation markers beta-tubulin-IV, Clara cell secretory protein, and Foxj1. Furthermore, changes in gene expression were recapitulated using an in vitro epithelial cell culture system and progressed independent of the host inflammatory response. Restoration of mature airway epithelium occurred in a pattern similar to epithelial cell differentiation and ciliogenesis in embryonic lung development characterized by sequential proliferation of undifferentiated cells, basal body production, Foxj1 expression, and beta-tubulin-IV expression. The effects of virus-induced alterations in morphology and gene expression on epithelial cell function were illustrated by decreased airway mucociliary velocity and impaired bacterial clearance. Similar changes in epithelial cell Foxj1 expression were also observed in human paramyxoviral respiratory infection. Taken together, these model systems of paramyxoviral respiratory infection mimic human pathology and identify epithelial cell Foxj1 expression as an early marker of epithelial cell differentiation, recovery, and function.

Computer-based collection of mammographic exposure data for quality assurance and dosimetry

PURPOSE

There is potentially more to quality assurance in mammography than the MQSA mandated tests. In this paper we describe a method of capturing individual mammogram technical parameters and the creation of new measures. These include the numbers of images required for each screening examination by technologist, median compression by technologist, and the radiation dose of the examination to the general population of patients.

METHOD/MATERIALS

With this method we describe a semiautomated method of the collection of technical data from mammography exposures. The data that are automatically created by the mammography unit are saved on a computer for later analysis. The method was used on 2738 consecutive screening mammography examinations and 13 621 exposures from one machine. Data were obtained from November 1998 through December 1999.

RESULTS

Using standard methods, the mean glandular dose (MGD) per exposure was 2.62 mGy (SD 1.2). The mean dose per bilateral screening examination was 6.53 mGy (SD 3.07), the median dose was 6.11 mGy, and the dose range was 1.13-34.23 mGy. Rhodium filtration was used for 18% of the exposures. The average and median breast thickness was 4.9 cm. The ACR phantom MGD for this machine was 2.44 mGy at 25 kVp, and 1.97 mGy at 26 kVp. The mean number of exposures for a bilateral mammogram was 4.9, and varied by a technologist from 4.7 to 5.2. The mean compression pressure varied by technologist from 13 to 30 lbs (58-134 N).

CONCLUSIONS

The mean dose per mammogram is slightly greater than the ACR phantom dose at 25 kVp. Almost five exposures were necessary for a standard bilateral examination, and this varied by technologist. The compression used also varied by technologist. The semiautomated collection of technical data can aid in maintaining an effective mammography QA program.

Pectoralis muscle performance during ascending and slow level flight in mallards (Anas platyrhynchos)

In vivo measurements of pectoralis muscle length change and force production were obtained using sonomicrometry and delto-pectoral bone strain recordings during ascending and slow level flight in mallards (Anas platyrhynchos). These measurements provide a description of the force/length properties of the pectoralis under dynamic conditions during two discrete flight behaviors and allow an examination of the effects of differences in body size and morphology on pectoralis performance by comparing the results with those of a recent similar study of slow level flight in pigeons (Columbia livia). In the present study, the mallard pectoralis showed a distinct pattern of active lengthening during the upstroke. This probably enhances the rate of force generation and the magnitude of the force generated and, thus, the amount of work and power produced during the downstroke. The power output of the pectoralis averaged 17.0 W kg(−)(1)body mass (131 W kg(−)(1)muscle mass) during slow level flight (3 m s(−)(1)) and 23.3 W kg(−)(1)body mass (174 W kg(−)(1)muscle mass) during ascending flight. This increase in power was achieved principally via an increase in muscle strain (29 % versus 36 %), rather than an increase in peak force (107 N versus 113 N) or cycle frequency (8.4 Hz versus 8.9 Hz). Body-mass-specific power output of mallards during slow level flight (17.0 W kg(−)(1)), measured in terms of pectoralis mechanical power, was similar to that measured recently in pigeons (16.1 W kg(−)(1)). Mallards compensate for their greater body mass and proportionately smaller wing area and pectoralis muscle volume by operating with a high myofibrillar stress to elevate mechanical power output.

First Reports of Aphelenchoides fragariae on Royal Fern and on Hosta and Other Hosts in South Carolina

In September 1999, royal ferns (Osmunda regalis L.) at a South Carolina wholesale nursery were found to be infected by foliar nematodes. Lesions were brown, vein-limited, and often fan shaped. As severity increased, affected leaflets became totally necrotic. Nematodes were extracted by excising and dicing symptomatic leaf sections and placing them in water for up to 24 h. Ten adult nematodes from each of two fern plants were examined microscopically and determined to be Aphelenchoides fragariae (Ritzema Bos) Christie. This is the first report of this nematode infecting royal fern. In August 1996, leaves from several cultivars of Hosta spp. with yellow to tan, vein-limited lesions were submitted from The South Carolina Botanical Garden (Clemson, SC) to the Clemson University Plant Problem Clinic for diagnosis. Nematodes were extracted and examined as described above and identified as A. fragariae. This is the first report of this nematode infecting Hosta spp. in South Carolina. Since 1996, foliar nematodes have been recovered from hostas at several wholesale nurseries in South Carolina. Aphelenchoides spp. also have been detected previously in commercially produced ornamental plants in South Carolina, including a Begonia sp. in 1988; Polygonum bistorta L. 'Super-bum' (snakeweed) in 1997; and a Polystichum sp. (holly fern) in 1997. All plants exhibited angular or vein-limited, necrotic lesions typical of foliar nematode infections.

First Report of the Teleomorph of an Oidium sp. Causing Powdery Mildew on Flowering Dogwood in South Carolina

Prior to 1994, powdery mildew had rarely been reported on flowering dogwood (Cornus florida) in the southeastern U.S. That year, and every year since, epiphytotics of powdery mildew have occurred. Leaf symptoms include distortion and necrotic areas on young leaves and an increase in red pigmentation surrounding infection sites. Young seedlings may be stunted by this disease and growth of older trees may be slowed (2). In early November, 1996, dogwood (C. florida) trees at 10 locations each in Anderson, Oconee, and Pickens counties in northwestern South Carolina were surveyed for the presence of powdery mildew. Leaves with signs of powdery mildew (white, powdery patches of mycelium, conidiophores, and conidia) were examined with a ×10 hand lens and leaves with cleistothecia were collected and taken back to the laboratory. Numerous leaves from each site were first examined at ×50 on a dissecting microscope to observe gross morphological features of cleistothecia. Then, approximately 10 cleistothecia from each of two sites were examined on a compound microscope at ×100 or higher to make further observations and measurements. Cleistothecial diameter ranged from 75.0 to 92.5 μm (average 81.8 μm). Appendages, which averaged 6 to 11 per cleistothecium, were 110 to 140 μm long (average 125.7 μm) or 1.54 times the cleistothecial diameter. The apices of appendages were dichotomously branched 2 to 3 times and the tips were distinctly re-curved. The stalks were aseptate and hyaline. Cleistothecia contained 3 to 5 asci. Each ascus contained 2 to 6 ascospores measuring 18 to 28 × 13 to 15 μm. Based on these characteristics, the teleomorph was tentatively identified as Microsphaera pulchra. Cleistothecia were found to be slightly smaller and the number of appendages fewer than Braun's lectotype (1), but these differences were judged to be of minor importance. Therefore, we conclude that the teleomorph of the Oidium sp., herein reported on flowering dogwood for the first time in South Carolina, is Microsphaera pulchra References: (1) U. Braun. Nova Hedwigia 89:1, 1987. (2) L. A. Klein et al. Plant Dis. 82:383, 1998.

Effects of age, breast density, ethnicity, and estrogen replacement therapy on screening mammographic sensitivity and cancer stage at diagnosis: review of 183,134 screening mammograms in Albuquerque, New Mexico

PURPOSE

To examine how common patient factors affect screening mammographic sensitivity and cancer stage at diagnosis.

MATERIALS AND METHODS

The authors used a population-based database of 183,134 screening mammograms and a statewide tumor registry to identify 807 breast cancers detected at screening mammography.

RESULTS

Sensitivity varied significantly with ethnicity, use of estrogen replacement therapy, mammographic breast density, and age. Sensitivity was 54% (13 of 24) in women younger than 40 years, 77% (121 of 157) in women aged 40-49 years, 78% (224 of 286) in women aged 50-64 years, and 81% (277 of 340) in women older than 64 years. Sensitivity was 68% (162 of 237) for dense breasts and 85% (302 of 356) for nondense breasts and 74% (180 of 244) in estrogen replacement therapy users and 81% (417 of 513) in nonusers. Sensitivity was most markedly reduced with the combination of dense breasts and estrogen replacement therapy use; there was little difference when only one factor was present. Median cancer size and the percentage of early cancers showed little change with any factors.

CONCLUSION

Age is a minor determinant of mammographic sensitivity in women aged 40 years or older. Sensitivity is substantially decreased with the combination of higher breast density and estrogen replacement therapy use. There was not a notable shift in cancer outcomes in the groups with lower mammographic sensitivity. These data do not support different screening recommendations in women aged 40-49 years or in estrogen replacement therapy users.

Thyroid palpation versus high-resolution thyroid ultrasonography in the detection of nodules

Detection of thyroid nodules by physical examination and high-resolution ultrasonography was compared using small groups of blinded, experienced physician examiners working with a sample of 2441 persons from Estonia, most of whom were Chernobyl nuclear reactor clean-up workers. A random subsample of 113 (5%) persons was subjected to triple control examinations with both physical examination and high-resolution ultrasonography. Positive high-resolution ultrasonographic findings were considerably more reproducible among different observers than were positive physical examination findings. Agreement between methods was poor. Nodules were found in 169 (6.9%) subjects by physical examination and in 249 (10.2%) subjects by high-resolution ultrasonography. Physical examination found only 53 (21%) of the 249 nodules found by high-resolution ultrasonography. High-resolution ultrasonography did not confirm the existence of 115 (68%) of the 169 nodules found by physical examination. Only 6.4% of nodules less than 0.5 cm in diameter, as based on high-resolution ultrasonographic results, were detected by physical examination. Physical examination detection improved with increasing nodule size but was still only 48.2% for nodules larger than 2 cm. Physical examination was relatively effective in detecting nodules in the isthmus of the thyroid gland but much less so for nodules in the upper pole of the gland. Clinical evaluation and epidemiologic studies of nodular thyroid disease stand to benefit from the greater sensitivity and specificity of ultrasonographic examinations.

Distinguishing hantavirus pulmonary syndrome from acute respiratory distress syndrome by chest radiography: are there different radiographic manifestations of increased alveolar permeability?

Hantavirus infection may cause diffuse air space disease, termed hantavirus pulmonary syndrome (HPS). The authors sought to determine if chest radiographs could differentiate HPS from typical acute respiratory distress syndrome (ARDS). The authors identified patients with either HPS (n = 11) or acute ARDS (n = 32) and selected the earliest chest radiograph showing diffuse airspace disease, and a chest radiograph taken 24 to 48 hours previously. Thoracic and general radiologists first viewed the chest radiograph showing diffuse air space disease, and ranked the likelihood that each case represented HPS versus ARDS. Afterward, readers viewed earlier chest radiographs and rescored each case. Receiver operating characteristic (ROC) curves from both scoring sessions were generated. The mean areas under the ROC curves for the entire group was 0.83 +/- 0.12 initially, and improved to 0.87 +/- 0.09 (p < 0.05) after viewing prior chest radiographs. Receiver operating characteristic curves of thoracic radiologists described greater areas than those of general radiologists both before and after viewing prior chest radiographs; 0.95 +/- 0.01 versus 0.78 +/- 0.08 (p < 0.05) and 96 +/- 0.02 versus 0.80 +/- 0.05 (p < 0.05). The mean sensitivity and specificity of chest radiograph interpretation for HPS was 86 +/- 13% and 74 +/- 11%, respectively. Chest radiographs can differentiate HPS from ARDS. Accuracy is improved by the use of serial radiographs and more highly trained readers. The chest radiograph findings may represent differences in the extent of alveolar epithelial damage seen in HPS and ARDS.

The New Mexico Mammography Project. Screening mammography performance in Albuquerque, New Mexico, 1991 to 1993

BACKGROUND

This project was designed to collect and link population-based mammography and breast carcinoma data to assess the performance of community mammography screening.

METHODS

Computerized data were collected from all radiology practices in Albuquerque, New Mexico. The data were linked by computer match to breast carcinomas in a statewide cancer registry. Analysis is based on 126,466 screening mammogram studies performed on 87,443 female residents of New Mexico between the ages of 35 and 84 by 5 radiology groups. Sensitivity, specificity, positive predictive value, and call back rates were calculated as indicators of the discriminative performance of mammography. Carcinoma size and stage distribution were analyzed as outcome measurements.

RESULTS

The computer match linked 634 breast carcinomas to the 126,466 screening mammogram series. The community-wide sensitivity was 79.9%, and specificity was 90.5%. The predictive value of an abnormal screen was 4.3%, and that of a biopsy recommendation result was 16.9%. The call back rate was 11.4%. The median invasive breast carcinoma size was 15 mm, 20.3% of carcinomas were in situ, 18.3% were lymph node positive, and 68.1% were Stage 0 or Stage 1.

CONCLUSIONS

Mass screening mammography as practiced in Albuquerque, New Mexico, is able to detect breast carcinomas at early, treatable stages. The stage distribution of carcinomas is similar to that seen in successful clinical trials. However, measures of mammography performance show lower sensitivity, more additional studies, and more biopsy recommendations in this community setting than have been reported by expert mammographers.

A sensitive RNase protection assay to detect transcripts from potentially functional human endogenous L1 retrotransposons

A high background of read-through transcripts from degenerate human L1 retrotransposons is present in almost all human cell types. This prevents the detection of RNA transcripts from potentially functional elements. To overcome this, we have developed an RNase protection assay based on the reconstructed consensus sequence for the 5' end of the major L1 family. In the human Ntera2D1 teratocarcinoma cell line, this assay readily detected L1 transcripts that were located primarily in the cytoplasm and where 20% were in filterable particles. By this assay, potentially functional L1 elements are also transcriptionally active in lymphocytes from some but not all normal individuals. Together with the full length protection product, there were three other discrete L1 RNAs, two of which (305 and 275 bases) were transcribed from the 5' end of the L1 element. These smaller L1 RNAs do not appear to be derived from transcripts from divergent L1 families but are either discrete shorter transcripts or specifically processed products from longer initial transcripts.

Case report. MR and CT appearance of cardiac hemangioma

We present a case of cardiac hemangioma in a symptomatic patient. MR and CT each have specific characteristics that should make one consider including or excluding this in the differential diagnosis of a cardiac tumor.

CT demonstration of a giant adrenal endothelial cyst of the angiomatous subtype

Adrenal cysts are uncommon lesions with only approximately 300 having been reported to date. Histologically, they are heterogeneous in nature with angiomatous endothelial cysts being quite rare. The computed tomography of a woman with a very large cyst of this variety displayed thin walls with a few septations and foci of soft tissue within. The possibility of a large cystic mass originating from the adrenal gland must be considered in the diagnosis when a large abdominal mass is encountered.

Hantavirus pulmonary syndrome: radiographic findings in 16 patients

PURPOSE

To characterize chest radiographic features of Hantavirus pulmonary syndrome.

MATERIALS AND METHODS

Initial and follow-up chest radiographs from 16 patients with confirmed Hantavirus pulmonary syndrome were reviewed for radiographic findings of either cardiogenic pulmonary edema or pulmonary edema due to increased permeability of the alveolar capillary membranes.

RESULTS

Findings indicative of interstitial edema were present more frequently (14 [88%] of 16 patients) than is typically seen in adult respiratory distress syndrome (5%). Alveolar flooding subsequently developed in 11 (69%) of 16 patients and was not the peripheral pattern usually seen in the acute phase of adult respiratory distress syndrome. Overall mortality was 43%. Lung specimens obtained at autopsy showed a pattern of endothelial leak with minimal epithelial injury.

CONCLUSION

The lung disease caused by Hantavirus in these patients may explain the findings of interstitial edema and central alveolar filling atypical of adult respiratory distress syndrome. Recognition of the radiographic pattern will be important in identifying this apparently widespread cause of increased permeability pulmonary edema.

Metallic foreign bodies in the orbits of patients undergoing MR imaging: prevalence and value of radiography and CT before MR

OBJECTIVE

The purpose of this study was to measure the prevalence of metallic foreign bodies in the orbits of 15,024 patients who were scheduled for MR imaging during a 4-year period and to determine if screening by plain radiography, CT, or both before MR imaging is efficacious.

MATERIALS AND METHODS

Records of 15,024 patients scheduled for MR imaging were reviewed. A total of 1593 patients who had identified themselves as being at risk for an intraorbital metallic foreign body had undergone plain radiography or CT of the orbits. Plain radiographs and/or CT scans of patients reported as having orbital metal were reviewed to confirm the presence of a metallic foreign body and to identify its location.

RESULTS

Metallic foreign bodies were discovered in 40 patients. Six of these patients had impaired vision in the involved eye. Ten patients had a metallic foreign body in or near the orbit but well away from the globe and were thought to be at low risk for movement of the foreign body as a result of MR imaging. The other 24 patients had metallic foreign bodies adjacent to or within the globe and were thought to be at risk for movement of the metallic foreign body as a result of MR imaging.

CONCLUSION

The prevalence of intraorbital metallic foreign bodies in our study population was low (0.27%). Even in those patients identified as being at risk, the prevalence was only 2.5%. Based on the number of MR examinations performed annually in the United States and on data indicating that no radiographic screening is performed at 5% of institutions, we extrapolate that more than 2400 patients with intraorbital metallic foreign bodies have undergone MR imaging since 1986 without report of injury. These data allow us to infer that the risk of eye damage for patients who have intraorbital metal is low and that radiographic screening before MR imaging is not needed as often as it is done.

Injuries associated with MR imaging: survey of safety records and methods used to screen patients for metallic foreign bodies before imaging

OBJECTIVE

The purpose of this study was to survey the methods used by academic institutions for identifying patients who might have metallic foreign bodies or other contraindications to MR imaging. We also sought to determine the types of MR-related injuries and any subsequent legal action that might have occurred at these institutions.

MATERIALS AND METHODS

A survey on these issues was mailed to 207 academic institutions listed in the American Medical Association's Directory of Graduate Medical Education Programs. Institutions that did not respond by mail were contacted by phone. The survey requested information on the use of questionnaires, plain radiography, CT, and metal detectors for screening potential MR imaging subjects, as well as on any MR-related injuries and subsequent legal action. Responses were entered into a data base and response percentages were calculated for each question.

RESULTS

The overall response rate for the survey was 99% (206/207). These 206 institutions have a total of 368 MR imaging units, with a mean number of 1.8 MR units per department (range, none to nine). Data from a total of 205 different sites revealed that all patients are screened before MR imaging with a written questionnaire at 93% of all institutions (190/205). For selected indications, 85% of departments (174/205) screen with plain film radiography of the orbits. For selected indications, 41% of facilities (83/205) screen with CT of the orbits. Patients are sometimes screened with a metal detector or magnetometer in 12% of the departments (24/205). Ten departments reported serious injuries relating to MR imaging. The most serious injury occurred when an oxygen tank near the magnet became a missile and struck a patient's face. Most injuries (nine of 14) were burns. Two institutions also reported adverse reactions to gadopentetate dimeglumine. Injuries prompted legal action against four of the 10 institutions. No injuries were related to intraorbital foreign bodies, vascular clips, or pacemakers in patients.

CONCLUSION

These data demonstrate the lack of consensus on screening protocols before MR imaging. Accidents are uncommon, but most accidents that do occur are potentially severe and easily preventable. We recommend that all patients be screened by a written questionnaire followed by oral questioning before imaging to determine those who are at risk. Specific questions should investigate the possibility that patients have ferromagnetic foreign bodies or implants anywhere in the body that are electrically, magnetically, or mechanically activated. All facilities must maintain a high state of vigilance in an effort to prevent iatrogenic burns and injuries from ferromagnetic missiles.

Modified-cytosine restriction-system-induced recombinant cloning artefacts in Escherichia coli

We have tested whether, and to what extent, recombinant clones from DNA segments with 5-methylation of cytosines recovered in methylation-restrictive (mcr+) hosts contain mutations. We constructed a model system in which the tetracycline-resistance-encoding gene (tet) from pBR322 was cloned into the plasmid pGEM3Zf+. The central region of tet was removed from the construct, methylated in vitro and then religated back into the unmethylated remainder of the construct. The central region of tet was either (1) methylated with a combination of four bacterial methyltransferases (M.AluI, M.HaeIII, M.HpaII plus M.HhaI) or (2) methylated with M.SssI which methylates at all CpG dinucleotides. These two protocols generated theoretical levels of DNA methylation in the central fragment of 10.5% and 33%, respectively. The construct was transformed into a series of isogenic (recA+) bacterial strains that were mcrA+ mcrB+C+, mcrA+ mcrB-C+, mcrA- mcrB+C+, mcrA- mcrB-C+ or mcrA- delta mcrBC, and also into a set of isogenic recA- derivatives of these strains. With the two methylation protocols, there was an average 48- and 141-fold reduction, respectively, in the number of transformants recovered from the recA+ mcr+ hosts compared with a methylation-tolerant host (mcr-). Of the clones recovered in recA+mcr+ hosts, > 20% of clones had an inactivating mutation in tet. The majority of such mutant clones contained deletions that frequently extended into the unmethylated portion of tet and even into the plasmid sequences beyond the end of the polylinker. With the recA- mcr+ hosts, effective restriction was much more stringent, rendering the plasmid containing the methylated segment effectively unclonable.(ABSTRACT TRUNCATED AT 250 WORDS)

Thyroid nodules in the population living around Chernobyl

OBJECTIVE

To determine the baseline incidence, prevalence, and characteristics of thyroid nodules in the population living around the Chernobyl nuclear power plant and to compare the findings with unexposed populations.

DESIGN

Prevalence study. Population samples from seven highly contaminated villages were compared with six nearby control villages of the same size and type. The data were obtained as part of the International Chernobyl Project conducted in 1990.

SETTING

The study was conducted 4.5 years after the Chernobyl reactor accident that released large quantities of radionuclides, including radioiodine.

PATIENTS OR OTHER PARTICIPANTS

Population samples of approximately 100 persons residing in both highly contaminated villages and control villages since the accident were compared. Individuals were selected on the basis of birth date as being 5, 10, 40, or 60 years old at the time of the study. All persons selected underwent a thyroid examination.

INTERVENTIONS

None.

MAIN OUTCOME MEASURES

Two main outcome measures were used, both for thyroid nodularity: clinical palpation and high-resolution ultrasonography.

RESULTS

There was no significant difference in thyroid nodularity between the study groups. Nodules were palpated in 0.7% of children and 2.9% of adults. Discrete nodules were found by ultrasonography in 0.5% of children and 14.9% of adults. Multinodular goiter was found in 3% of adults. Nodules were more common in females.

CONCLUSIONS

Four and a half years after the Chernobyl accident, the incidence, prevalence, and characteristics of thyroid nodules were the same in population samples from both highly contaminated and control settlements and similar to results reported for unexposed populations in other countries.

Differential expression of neural cell adhesion molecule and cadherins in pancreatic islets, glucagonomas, and insulinomas

The endocrine cells of the pancreas develop from the endoderm and yet display several characteristics of a neuronal phenotype. During embryonic life, ductal epithelial cells give rise to first the glugagon-producing cells (alpha-cells) and then cells that express insulin (beta-cells), somatostatin (delta-cells), and pancreatic polypeptide (PP-cells) in a sequential order. The endocrine cells are believed to arise from a stem cell with neuronal traits. The developmental lineage from a common neuron-like progenitor is evidenced by: transient coexpression of more than one cell type-specific hormone in immature cells, expression of neuronal markers during islet cell development, and the pluripotentiality of clones of insulinoma cells to develop into cells expressing other islet cell hormones. The four mature endocrine cell types assume a particular organization within the islets of Langerhans in a process where cell adhesion molecules are involved. In this study we have analyzed the expression of neural cell adhesion molecule (NCAM) and cadherin molecules in neonatal, young, and adult rat islet cells as well as in glucagonomas and insulinomas derived from a pluripotent rat islet cell tumor. Whereas primary islet cells at all ages express unsialylated NCAM and E-cadherin, as do insulinomas, the glucagonomas express the polysialylated NCAM, which is characteristic for developing neurons. The glucagonomas also lose E-cadherin expression and instead express a cadherin which is similar to N-cadherin in brain. Insulinoma cells express E-cadherin but differ from primary islet cells by expressing a second cadherin molecule, which is similar to N-cadherin. The expression of NCAM and cadherin isoforms in the glucagonoma suggest that this transformed alpha-cell type has converted to an immature phenotype with strong neuronal traits, reflecting the early palce of glucagon-producing cells in the islet cell lineage. In contrast, insulinoma cells are more islet-like in their phenotype and show less neuronal traits.

Magnetic resonance imaging of musculoskeletal tumors

The Scientific Board of the California Medical Association presents the following inventory of items of progress in radiology. Each item, in the judgment of a panel of knowledgeable physicians, has recently become reasonably firmly established, both as to scientific fact and important clinical significance. The items are presented in simple epitome, and an authoritative reference, both to the item itself and to the subject as a whole, is generally given for those who may be unfamiliar with a particular item. The purpose is to assist busy practitioners, students, researchers, or scholars to stay abreast of these items of progress in radiology that have recently achieved a substantial degree of authoritative acceptance. Whether in their own field of special interest or another. The items of progress listed below were selected by the Advisory Panel to the Section on Radiology of the California Medical Association, and the summaries were prepared under its direction.

Eosinophilia-myalgia syndrome: findings on chest radiographs in 18 patients

Findings on chest radiographs of 18 patients with the eosinophilia-myalgia syndrome were compared and correlated with peak eosinophil counts. Nine patients had normal chest radiographs. Of the nine patients with abnormal chest radiographs, three had fine, irregular linear opacities in the lungs (the opacities were most noticeable at the bases); three had similar irregular linear opacities and pleural effusions; and three had pleural effusions and confluent opacities. One patient demonstrated an enlarged heart; no pulmonary edema was seen in this patient or in any others. Although the mean recorded eosinophil cell counts were higher in those patients with abnormal chest radiographs (6,340 vs 5,454/mm3 [6.3 vs 5.4 x 10(9)/L]), the difference was not statistically significant.

Revised genomic consensus for the hypermethylated CpG island region of the human L1 transposon and integration sites of full length L1 elements from recombinant clones made using methylation-tolerant host strains

Efficient recovery of clones from the 5' end of the human L1 dispersed repetitive elements necessitates the use of deletion mcr- host strains since this region contains a CpG island which is hypermethylated in vivo. Clones recovered with conventional mcr+ hosts seem to have been derived preferentially from L1 members which have accumulated mutations that have removed sites of methylation. We present a revised consensus from the 5' presumptive control region of these elements. This revised consensus contains a consensus RNA polymerase III promoter which would permit the synthesis of transcripts from the 5' end of full length L1 elements. Such potential transcripts are likely to exhibit a high degree of secondary structure. In addition, we have determined the flanking sequences for 6 full length L1 elements. The majority of full length L1 clones show no convincing evidence for target site duplication in the insertion site as commonly observed with truncated L1 elements. These data would be consistent with two mechanisms of integration of transposing L1 elements with different mechanisms predominating for full length and truncated elements.

Osteomyelitis: sensitivity of 0.064 T MRI, three-phase bone scanning and indium scanning with biopsy proof

We compared the ability of magnetic resonance imaging (MRI) using a 0.064 T permanent magnet, three-phase bone scanning, and indium-labeled white blood cell (111In-WBC) scanning, to diagnose osteomyelitis. Twenty-three patients underwent biopsy. All patients were examined at presentation with all three modalities. Sensitivities for each modality were calculated using biopsy as a gold standard. The results were 72% for MRI, 68% for bone scan, and 45% for 111In-WBC. Specificities were not calculated because of lack of negative biopsies. MRI was as sensitive as bone scanning in the diagnosis of osteomyelitis. All modalities had lower than previously reported sensitivities for imaging osteomyelitis.

Scintigraphic appearance of uncommon soft-tissue osteogenic sarcoma metastases

The advent of improved chemotherapy has changed the natural course of osteosarcoma. The role of bone scintigraphy in the workup of metastatic osteosarcoma is being re-evaluated. Extra-osseous osteogenic sarcoma metastases, particularly pulmonary metastases, are known to accumulate bone-avid agents. In this case, there is also uptake by noncalcified metastases to the brain and to soft tissues of the leg and arm which has not been previously reported. Correlation with computed tomography and magnetic resonance imaging is made.

Osteoporosis: diagnosis by plain chest film versus dual photon bone densitometry

Readers of chest radiographs often comment on the presence of osteoporosis. We have hypothesized that diagnoses of osteoporosis from chest films are not reliable even when made by experienced radiologists. To test this hypothesis, we had nine radiologists estimate the degree of bone density seen on 45 lateral chest films. We compared their estimates of bone density to the results of dual photon bone densitometry of the lumbar spine. We found that there was little ability to accurately diagnose osteoporosis by chest film since the group of nine readers achieved accuracies ranging from 0.59 to 0.64. Therefore, we feel it is unjustified to comment upon the presence or absence of osteoporosis on the basis of chest films.

Localization of adrenal and extra-adrenal pheochromocytomas by magnetic resonance imaging

We found magnetic resonance imaging helpful in the localization of both an adrenal and an extra-adrenal pheochromocytoma, since these tumors produced a high-intensity "light bulb" image. MRI is an excellent method for localizing pheochromocytomas because it detects adrenal and extra-adrenal pheochromocytomas missed by computerized tomography and adrenal-renal ultrasonography, and because the high-intensity MRI signal generated by pheochromocytomas is useful in differentiating them from nonfunctioning adrenal masses in hypertensive patients.

Avascular necrosis of the capitate demonstrated on a 0.064 T magnet

We report the first case of avascular necrosis of a carpal bone to be imaged on a 0.064 Tesla magnet, one of the lowest field strength magnetic resonance imaging systems currently available.

CT of emphysematous gastritis

Emphysematous gastritis is a serious, often fatal condition. It is the result of destruction of the mucosal membrane with subsequent bacterial invasion of the stomach. We have encountered two cases at CT. Recognition is important since early intervention may be lifesaving.

Technetium-99m RBC bleeding images in normal subjects: confusion with gastrointestinal bleeding sites

The normal appearance of a gastrointestinal bleeding study using labeled red blood cells has been discussed frequently, but the actual appearance is not well known. In this atlas article, the authors report on unusual findings in non-bleeding subjects and have tabulated the visualization of various structures. Vascular structures other than the aorta and inferior vena cava were seen in 42 of 48 patients. One or both kidneys were seen in 10 (21%) of 48 patients. The urinary bladder was seen in 23 (48%) of 48 patients, although gastric activity caused by free pertechnetate was never observed.

MRI of peripheral neurofibromas in children

Magnetic resonance imaging was performed as a preoperative examination in three children with neurofibromatosis and soft-tissue plexiform neurofibromas. In all three patients, MRI showed more widespread soft tissue involvement than was suspected clinically including extension towards the spine in each case. Patient management was changed in each case after MRI was performed.

MRI in the evaluation of spina bifida patients in the remote period after meningomyelocele repair

MRI was performed on 22 patients ranging in age from 3 months to 16 years who had closure of their meningomyelocele shortly after birth. These patients had developed new clinical findings suggestive of spinal cord dysfunction. MRI showed low placement of the spinal cord in all 22. Six patients had lipomas, five had diastematomyelia and six had hydromyelia. Four patients had an obviously dysplastic terminal cord.

Hemorrhagic adrenal metastases: CT findings

Adrenal hemorrhage secondary to metastases is uncommon. We have encountered four such cases that presented as large adrenal masses. In all cases the CT findings were of an inhomogeneous mixed-density adrenal mass with extensive perirenal changes suggestive of perirenal hemorrhage or mass. When such a lesion is seen, hemorrhagic adrenal metastases should be considered. Fluid may be of high density, suggestive of hemorrhage. However, as the adrenal is in the perinephric space, hemorrhage from any cause (trauma, metastases, or anticoagulant) in the adrenal gland will gravitate into the perinephric space.

Effect of a 1.5 Tesla magnetic field on Greenfield filters in vitro and in dogs

The authors have tested four Greenfield filters for deflection in a 1.5 Tesla magnetic field and found large variations in the amount of deflection among filters. They also placed two filters in dogs and checked the filter for migration by taking radiographs before and after magnetic resonance imaging (MRI) scans. They found no evidence of migration. They conclude that, while most Greenfield filters respond to a magnetic field, the chance of migration of a filter because of an MRI scan is small. Therefore, MRI scanning of patients with Greenfield filters has little risk.

Spine: device to facilitate surface coil MR imaging

A device was constructed to allow rapid adjustment of the position of a surface coil in magnetic resonance (MR) imaging of the spine. The device consists of two sheets of acrylic plastic and a movable sled. The surface coil is placed on the sled and can be precisely moved superiorly or inferiorly with a cord attached to the sled. The device can save approximately 30 minutes during MR imaging of the entire spine and increases patient comfort and cooperation.

Indium-111 leukocyte accumulation in submandibular gland saliva as a cause for false-positive gut uptake in children

Unexplained false-positive accumulation of In-111 leukocyte in the gastrointestinal tract has been reported previously. In a pediatric population, uptake in the submandibular gland was noted in 19 of 42 children. This is believed to be a normal finding in children that is not seen in adults. In some of these 19 children, unexplained gastrointestinal activity was also noted. Saliva from a patient with false-positive gastrointestinal uptake and positive submandibular activity was positive for In-111. One suggested cause of unexplained gut activity may be secondary to swallowed activity in the saliva from the normal submandibular activity in children.

Incidence of subcortical lesions not increased in nonarteritic ischemic optic neuropathy on magnetic resonance imaging

We performed magnetic resonance imaging on nine patients with nonarteritic ischemic optic neuropathy and 11 control patients with sensorineural hearing loss and suspected acoustic neuroma. We then counted the number of subcortical lesions in each patient, which may represent an index of generalized cerebral vascular disease. Although patients in the ischemic optic neuropathy group had an average of 3.2 subcortical lesions and those in the control group had an average of 0.9 lesions, this difference was not significant. Based on the presence of subcortical lesions, patients with nonarteritic ischemic optic neuropathy do not appear to have an increased incidence of generalized cerebral vascular disease.