Biomedical subjects
D Richardson
Publications and source records attributed to D Richardson.
Adrenocorticotropin-secreting carcinoid tumour identified and treated 12 years after presentation with Cushing's syndrome.
A case of Cushing's syndrome due to an adrenocorticotropin (ACTH) secreting bronchial carcinoid tumour is described. Endocrine assessment suggested ectopic ACTH syndrome, but imaging revealed no tumour. Bilateral adrenalectomy was performed, and computed tomographic scans of chest and abdomen were performed annually. A small nodule became apparent in the right lung 12 years after the presentation, which postoperatively was confirmed as the bronchial carcinoid tumour responsible for the ectopic ACTH syndrome.
Student perceptions and learning outcomes of computer-assisted versus traditional instruction in physiology.
This study compared student perceptions and learning outcomes of computer-assisted instruction against those of traditional didactic lectures. Components of Quantitative Circulatory Physiology (Biological Simulators) and Mechanical Properties of Active Muscle (Trinity Software) were used to teach regulation of tissue blood flow and muscle mechanics, respectively, in the course Medical Physiology. These topics were each taught, in part, by 1) standard didactic lectures, 2) computer-assisted lectures, and 3) computer laboratory assignment. Subjective evaluation was derived from a questionnaire assessing student opinions of the effectiveness of each method. Objective evaluation consisted of comparing scores on examination questions generated from each method. On a 1-10 scale, effectiveness ratings were higher (P < 0.0001) for the didactic lectures (7.7) compared with either computer-assisted lecture (3.8) or computer laboratory (4.2) methods. A follow-up discussion with representatives from the class indicated that students did not perceive computer instruction as being time effective. However, examination scores from computer laboratory questions (94.3%) were significantly higher compared with ones from either computer-assisted (89.9%; P < 0.025) or didactic (86.6%; P < 0.001) lectures. Thus computer laboratory instruction enhanced learning outcomes in medical physiology despite student perceptions to the contrary.
Cytosolic Ca2+ and adenylyl cyclase responses in phenotypically distinct pulmonary endothelial cells.
Pulmonary microvascular endothelium forms a tighter barrier than does pulmonary artery endothelium; the mechanism of this important phenotypic difference is uncertain. We examined two regulators of endothelial permeability, cytosolic Ca2+ concentration ([Ca2+]i) and adenosine 3',5'-cyclic monophosphate (cAMP), in microvascular (PMVEC) and pulmonary conduit artery (PAEC) endothelium. Both resting and stimulated [Ca2+]i were lower in PMVEC compared with PAEC (resting [Ca2+]i, 94 +/- 7 vs. 123 +/- 8 nM; ATP-stimulated peak, 1.04 +/- 0.14 vs. 1.98 +/- 0.13 microM). Sustained Ca2+ transients in response to either ATP or thapsigargin were reduced in PMVEC compared with PAEC (ATP, 199 +/- 22 vs. 411 +/- 43 nM; thapsigargin, 195 +/- 13 vs. 527 +/- 65 nM), suggesting reduced Ca2+ influx in PMVEC. Reduced Ca2+ influx in PMVEC was confirmed by Mn2+ quenching and patch-clamp experiments. mRNA for Ca(2+)-inhibitable and protein kinase C-stimulated adenylyl cyclases was detected in both cell types. Whereas ATP caused a [Ca2+]i-mediated decrease in cAMP in PAEC, ATP caused a protein kinase C-mediated increase in cAMP in PMVEC. We conclude that PMVEC express a unique phenotype that favors enhanced barrier function through attenuated Ca2+ influx and preservation of cAMP content.
The effect of botulinum toxin on hand function after incomplete spinal cord injury at the level of C5/6: a case report.
OBJECTIVE: To investigate the benefits of the focal use of botulinum toxin in spasticity in the forearm seen after incomplete spinal cord injury. DESIGN: A single case study with standardized assessment before and at three-week intervals after injection. INTERVENTION: EMG-guided selective injection of botulinum toxin. SUBJECT: A 23-year-old man, 18 months post injury. MEASURES: Rivermead Motor Assessment; grip strength; Jebsen hand tests; visual analogue scale; Ashworth spasticity scale. RESULTS: Weakness was seen as expected with some functional losses, but the patient made gains in the areas of concern: shaking hands, typing, using the hand to drink. These gains were sustained at 12 weeks. CONCLUSION: Selective use of botulinum toxin to weaken muscles can lead to functional benefit.
Intraosseous hemangiosarcoma with metastasis in a three-month-old llama.
Explore the source record for details and available documents.
Reply to comments on "A reevaluation of cancer incidence near the Three Mile Island".
Explore the source record for details and available documents.
A reevaluation of cancer incidence near the Three Mile Island nuclear plant: the collision of evidence and assumptions.
Previous studies concluded that there was no evidence that the 1979 nuclear accident at Three Mile Island (TMI) affected cancer incidence in the surrounding area; however, there were logical and methodological problems in earlier reports that led us to reconsider data previously collected. A 10-mile area around TMI was divided into 69 study tracts, which were assigned radiation dose estimates based on radiation reading and models of atmospheric dispersion. Incident cancers from 1975 to 1985 were ascertained from hospital records and assigned to study tracts. Associations between accident doses and incidence rates of leukemia, lung cancer, and all cancer were assessed using relative dose estimates calculated by the earlier investigators. Adjustments were made for age, sex, socioeconomic characteristics, and preaccident variation in incidence. Considering a 2-year latency, the estimated percent increase per dose unit +/- standard error was 0.020 +/- 0.012 for all cancer, 0.082 +/- 0.032 for lung cancer, and 0.116 +/- 0.067 for leukemia. Adjustment for socioeconomic variables increased the estimates to 0.034 +/- 0.013, 0.103 +/- 0.035, and 0.139 +/- 0.073 for all cancer, lung cancer, and leukemia, respectively. Associations were generally larger considering a 5-year latency, but were based on smaller numbers of cases. Results support the hypothesis that radiation doses are related to increased cancer incidence around TMI. The analysis avoids medical detection bias, but suffers from inaccurate dose classification; therefore, results may underestimate the magnitude of the association between radiation and cancer incidence. These associations would not be expected, based on previous estimates of near-background levels of radiation exposure following the accident.
Trends in fatal occupational injuries and industrial restructuring in North Carolina in the 1980s.
OBJECTIVES: This study examined the relationship between changes in employment in North Carolina in the 1980s and fatal occupational injury rates. METHODS: Unintentional fatal occupational injuries (n = 1989) in North Carolina between 1978 and 1991 were identified via the medical examiner's system. RESULTS: Overall fatal injury rates declined during the 1980s, but rates increased 9.6% per year among manufacturing industries that declined in employment size; rates fell among service sector and manufacturing industries that grew. CONCLUSIONS: Increasing occupational fatal injury rates accompanied the decline in workforce in North Carolina's traditional, labor-intensive manufacturing industries during the 1980s, while service sector and expanding manufacturing industries have experienced declining fatal injury rates.
ECG and cardiac enzymes changes associated with subarachnoid hemorrhage.
Explore the source record for details and available documents.
Evidence of deteriorating semen quality in the United Kingdom: birth cohort study in 577 men in Scotland over 11 years.
OBJECTIVE: To determine whether the quality of semen has changed in a group of over 500 Scottish men born between 1951 and 1973. DESIGN: Retrospective review of data on semen quality collected in a single laboratory over 11 years and according to World Health Organisation guidelines. SETTING: Programme of gamete biology research funded by Medical Research Council. SUBJECTS: 577 volunteer semen donors. Of these, 171 were born before 1959, 120 were born in 1960-4, 171 in 1965-9, and 115 in 1970-4. MAIN OUTCOME MEASURES: Conventional criteria of semen quality including semen volume (ml), sperm concentration (10(6)/ml), overall motility (% motile), total number of sperm in the ejaculate (10(6)), and total number of motile sperm in the ejaculate (10(6)). RESULTS: When the four birth cohort groups were compared a later year of birth was associated with a lower sperm concentration, a lower total number of sperm in the ejaculate, and a lower number of motile sperm in the ejaculate. The median sperm concentration fell from 98x10(6)/ml among donors born before 1959 to 78x10(6)/ml among donors born after 1970 (P=0.002). The total number of sperm in the ejaculate fell from 301x10(6) to 214x10(6) (P=0.0005), and the total number of motile sperm in the ejaculate fell from 169.7x10(6) to 129.0x10(6) (P=0.0065). CONCLUSION: This study provides direct evidence that semen quality is deteriorating, with a later year of birth being significantly associated with a reduced number of sperm in adult life.
Crystal structures of a single coiled-coil peptide in two oligomeric states reveal the basis for structural polymorphism.
Each protein sequence generally adopts a single native fold, but the sequence features that confer structural uniqueness are not well understood. To define the basis for structural heterogeneity, we determined the high resolution X-ray crystal structures of a single GCN4 leucine-zipper mutant (Asn 16 to aminobutyric acid) in both dimeric and trimeric coiled-coil conformations. The mutant sequence is accommodated in two distinct structures by forming similarly-shaped packing surfaces with different sets of atoms. The trimer structure, in comparison to a previously-characterized trimeric mutant with substitutions in eight core residues, shows that the twist of individual helices and the helix-helix crossing angles can vary significantly to produce the most favoured packing arrangement.
The successful conversion to Tacrolimus (FK506) of a renal transplant recipient with cyclosporin-induced haemolytic-uraemic syndrome.
Explore the source record for details and available documents.
Reproducibility of MEG auditory evoked field source localizations in normal human subjects using a seven-channel gradiometer.
Magnetoencephalographic (MEG) auditory evoked fields (EF) were recorded from 12 normal adult subjects over both hemispheres on two separate occasions at least one week apart using a seven-channel second-order gradiometer. Stimuli were computer-generated at 25-msec duration, 1 kHz tone pips. Responses to 100 stimuli were averaged, and source estimates with confidence intervals were computed, for the 100-msec latency auditory EF component, termed M100. Root-mean-squared (rms) differences in x, y, and z locations were approximately 0.7 cm on the two occasions; strength and orientation differences were 18 nA-m and 11 degrees, respectively. This spatial accuracy using a seven-channel instrument, compares favorably with other currently available technologies for localization of brain function.
Necrotizing cerebritis in an allogeneic bone marrow transplant recipient due to Cladophialophora bantiana.
We describe a necrotizing cerebritis in an allogeneic bone marrow transplant recipient caused by the neurotropic, dematiaceous fungus Cladophialophora bantiana. The patient presented 7 months after bone marrow transplantation with fever and sudden onset of left-sided weakness, followed shortly by cranial nerve III and VI palsies. The patient had a lesion (3.0 by 2.0 by 2.0 cm) of the right midbrain with extension to the pons, the left brain stem, and the right superior and the middle cerebellar peduncles. The diagnosis was made by microscopic examination and culture of a brain biopsy.
Using situational physiology in a didactic lecture setting.
This project used the approach of "human situations" to teach about the cardiovascular system within an undergraduate physiology course (PGY 412). About two-thirds of the students had previously taken a college-level physiology course (sophisticated), whereas one-third had not (naive). Nine didactic lectures were organized around the common human situations of orthostasis, blood donation, and exercise. For acceptance evaluation, the students were given a questionnaire consisting of six expectation statements (e.g., compared with other life science courses, I expect that I will better understand the material) and asked to rate the degree to which they agreed with each statement on a scale of 1 to 5. On completion of the lectures, the students were given a questionnaire asking them to compare experiences with expectations. Experiences were significantly less than expectations for naive (P < 0.05) but not for sophisticated students. On a scale of 1 to 5, sophisticated students preferred the situations approach more than did naive students (3.1 vs 2.4; P < 0.066). For performance evaluation, the students were given a set of questions used by the author in a previous PGY 412 course presented by traditional didactic lectures. There were no significant differences between present and previous scores (77 vs. 79%; P > 0.16). Furthermore, there were no significant differences between naive and sophisticated students in cardiovascular examination scores (P > 0.608) or in total course scores (P > 0.523). These results indicate that didactic lectures based on situational physiology will yield a performance outcome equivalent to traditional lectures. However, naive students may have difficulty with the procedure and require extra attention.
The perceptions of African-American physicians concerning their treatment by managed care organizations.
Explore the source record for details and available documents.