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Biomedical subjects

J N Scott

Publications and source records attributed to J N Scott.

At least 19 recordsLinked to original sources
PubMed2000

Using QuickTime virtual reality objects in computer-assisted instruction of gross anatomy: Yorick--the VR Skull.

QuickTime virtual reality (QTVR) is a software technology that creates, on a normal computer screen, the illusion of holding and turning a three-dimensional object. QTVR is a practical photo-realistic virtual reality technology that is easily implemented on any current personal computer or via the Internet with no special hardware requirements. Because of its ability to present dynamic photo-quality images, we reasoned that QTVR can provide a more realistic presentation of anatomic structure than two-dimensional atlas pictures and facilitate study of specimens outside the dissection lab. We created QTVR objects, using portions of the skull, and incorporated them into an instructional program for first-year medical students. To obtain images, the bones of the skull were mounted on a rotating table, and a digital camera was positioned on a swinging arm so that the focal point remained coincident with the rotational center of the object as the camera was panned through a vertical arc. Digital images were captured at intervals of 10 degrees rotation of the object (horizontal pan). The camera was then swung through an arc with additional horizontal pan sequences taken at 10 degrees intervals of vertical pan. The images were edited to place the object on a solid black background, then assembled into a linear QuickTime movie. The linear movie was processed to yield a QTVR object movie that can be manipulated on vertical and horizontal axes using the mouse. QTVR movies were incorporated into an interactive environment that provided labeling, links to text-based information and self-testing capabilities. This program, Yorick-the VR Skull, has been used in our first-year medical and graduate gross anatomy courses for the past two years. Results of student evaluation of the program indicate that this QTVR-based program is an effective learning tool that is well received by students.

Anatomy↗
PubMed1999

Correlation of neurologic dysfunction with CT findings in early acute stroke.

OBJECTIVE: To determine the frequency of early computed tomographic (CT) findings of ischemia and their relationship to symptom duration and neurologic dysfunction within 3 hours of ischemic stroke. METHODS: The CT scans of 39 acute stroke patients were evaluated for signs of early ischemic change within 3 hours of symptom onset and without knowledge of the patient's neurologic deficit or results of a 24 hour follow-up post-thrombolysis CT. Early CT signs of acute ischemic change or thromboembolism were hypoattenuation of the insular ribbon, obscuration of the lentiform nucleus, cortical hypodensity/effacement, and hyperdense middle cerebral artery sign. RESULTS: Signs of acute ischemic change were seen on the baseline scan in 25/39 patients (64%). Hypoattenuation of the insular ribbon was seen in 11 patients, obscuration of the lentiform nucleus in 13, cortical hypodensity/effacement in 13, and hyperdense middle cerebral artery sign in 7. The prevalence of early ischemic signs was directly associated with increasing neurologic disability at the time of presentation. No clear relationship existed between symptom duration and the presence of CT signs. CONCLUSIONS: Evidence of cerebral ischemia is frequently seen on CT within 3 hours of symptom onset. The degree of neurologic disability correlates with CT signs of ischemia.

Adult↗
PubMed1999

Neurofilament and tubulin gene expression in progressive experimental diabetes: failure of synthesis and export by sensory neurons.

In human and experimental diabetes, the relationship between molecular abnormalities in perikarya of sensory neurons and structural abnormalities in their distal axons is largely unexplored. In this study we examined neurofilament (Nf) and tubulin messenger RNA (mRNA) expression and their incorporation into distal sensory axons during progressive streptozotocin-induced diabetes in rats. After 2 and 6 months of diabetes, we measured mRNA levels of all three Nf subunits, B50 [growth associated protein-43 (GAP-43)] and alpha-tubulin in L4-L6 dorsal root ganglia using Northern analysis. The same animals underwent morphometric studies of myelinated fibres by light microscopy and quantitative analysis of Nf and microtubule numbers and density within sural myelinated and unmyelinated axons. Multifibre in vivo sensory and motor conduction nerve recordings confirmed slowing of conduction velocities in diabetic rats indicating experimental neuropathy. mRNA levels for the three Nf subunits, B50 (GAP-43) and alpha-tubulin were unchanged from controls at 2 months, but were decreased by 26-46% at 6 months. These changes accompanied declines in Nf numbers and densities within large myelinated sensory axons, and Nf numbers in unmyelinated fibres by 6 months. Microtubule numbers and densities were similarly reduced in large myelinated axons, and microtubule numbers reduced in small myelinated and unmyelinated axons in diabetes at 6, but not 2 months. Axonal atrophy was observed in unmyelinated fibres at 6 months. Our findings indicate that decreased mRNA expression of cytoskeletal proteins in sensory neurons accompanies a reduction in their incorporation into distal axons. These changes imply that there is a direct link between pathological changes in the sensory neuron and alterations of its distal branches from experimental diabetes. The changes in gene expression in diabetes are unique and differ from those that develop after axotomy.

Animals↗
PubMed1999

Which glioblastoma multiforme patient will become a long-term survivor? A population-based study.

In this clinical and histopathological study, the frequency of long-term glioblastoma multiforme (GBM) survivors (LTGBMSs) was determined in a population-based study. The Alberta Cancer Registry was used to identify all patients diagnosed with GBM in Alberta between January 1, 1975, and December 31, 1991. Patient charts were reviewed and histology reexamined. LTGBMSs were defined as GBM patients surviving 3 years after diagnosis. Each LTGBMS was compared with 3 age-, sex-, and year of diagnosis-matched controls, and patient/treatment or tumor characteristics that predicted long-term survival were determined. There were 689 GBMs diagnosed in the study period; 15 (2.2%) of these patients survived 3 years. LTGBMSs (average age, 43.5 +/- 3.3 years) were significantly younger when compared with all GBM patients (average age, 53.0 +/- 0.56 years). LTGBMSs had a higher Karnofsky Performance Status score at diagnosis compared with controls. LTGBMSs were much more likely to have had a gross total resection and adjuvant chemotherapy than control GBM patients. Tumors from LTGBMSs tended to have fewer mitoses and a significantly lower Ki-67 cellular proliferation index compared with controls. Radiation-induced dementia was common and disabling in LTG-BMSs. In conclusion, conventionally treated GBM patients in an unselected population have a very small chance of long-term survival. The use of aggressive surgical resection and adjuvant chemotherapy may make long-term survival more likely in GBM patients if their performance status is high at diagnosis.

Adolescent↗
PubMed1998

Long-term glioblastoma multiforme survivors: a population-based study.

BACKGROUND: Long-term glioblastoma multiforme survivors (LTGBMS) are uncommon. The frequency which these occur in an unselected population and factors which produce these unusually long survivors are unknown. OBJECTIVES: To determine in a population-based study 1) the frequency of LTGBMS in a population and 2) identify which patient, treatment or tumor characteristics would predict which glioblastoma (GBM) patient would become a LTGBMS. METHODS: The Alberta Cancer Registry was used to identify all patients diagnosed with GBM in southern Alberta between 1/1/75-12/31/91. Patient charts were reviewed and histology re-examined by a blinded neuropathologist. LTGBMS were defined as GBM patients surviving > or = 3 years after diagnosis. Each LTGBMS was compared to three age-, gender-, and year of diagnosis-matched controls to compare patient, treatment, and tumor factors to GBM patients without long-term survival. RESULTS: There were 279 GBMs diagnosed in the study period. Five (1.8%) survived > or = three years (range, 3.2-15.8 years). Seven additional long-term survivors, who carried a diagnosis of GBM, were excluded after neuropathologic review; the most common revised diagnosis was malignant oligodendroglioma. LTGBMS (avg. age = 45 years) were significantly younger when compared to all GBM patients (avg. age = 59 years, p = 0.0001) diagnosed in the study period. LTGBMS had a higher KPS at diagnosis (p = 0.001) compared to controls. Tumors from LTGBMS tended to have fewer mitoses and a lower Ki-67 cellular proliferative index compared to controls. Radiation-induced dementia was common and disabling in LTGBMS. CONCLUSIONS: These data highlight the dismal prognosis for GBM patients who have both a short median survival and very small chance (1.8%) of long-term survival. The LTGBMS were younger, had a higher performance status, and their tumors tended to proliferate less rapidly than control GBM patients. When long-term survival does occur it is often accompanied by severe treatment-induced dementia.

Adult↗
PubMed1998

Critical thinking: change during medical school and relationship to performance in clinical clerkships.

The development of critical thinking, the ability to solve problems by assessing evidence using valid inferences, abstractions, and generalizations, is one of the global goals advocated by most medical schools. This study determined changes in critical thinking skills between entry and near the end of the third year of medical school, assessed the predictive ability of a test of critical thinking skills, and assessed the concurrent validity of clerkship components and final grade. The Watson-Glaser Critical Thinking Assessment (WGCTA) was administered to one class of students at entry to medical school and near the end of year 3. Performance data for those students who completed their clinical clerkships on schedule were also recorded. Critical thinking improved modestly but significantly from entry to medical school to near the end of year 3. The ability of a critical thinking test to predict clerkship performance was limited; the correlation between WGCTA total score at entry and the components and final grade of five major clerkships ranged from near 0 to 0.34. The concurrent validity of clerkship components and final grade was also limited; correlations with WGCTA total score near the end of year 3 ranged between 0.08 and 0.49. The correlation between WGCTA total score and United States Medical Licensing Examination Step 2 was higher at year 3 than at medical school entry. Critical thinking skills improve moderately during medical school. Used alone, tests of critical thinking may be of limited value in predicting which students will be successful in clinical clerkships. Clerkship evaluation components and final grade have limited concurrent validity when a test of critical thinking is the criterion.

Clinical Clerkship↗
PubMed1995

Axonal atrophy in aging is associated with a decline in neurofilament gene expression.

Neurofilaments (Nfs) are major determinants of axonal caliber. Nf transcript levels increase during development and maturation, and are associated with an increase in Nf protein, Nf numbers, and caliber of axons. With aging there is axonal atrophy. In this study we asked whether the axonal atrophy of aging was associated with a decline in Nf transcript expression, Nf protein levels, and Nf numbers. Expression of transcripts for the three Nf subunits was evaluated in dorsal root ganglia (DRG) of Fischer-344 rats aged 3-32 months by Northern and in situ hybridization. There was an approximately 50% decrease in Nf subunit mRNA levels in DRG of aged (> 23 months) as compared to young and mature (3 and 12 months) rats, whereas expression of another neuronal mRNA, GAP-43, showed no decline. Western analysis showed a corresponding decrease in Nf subunit proteins and no decline in GAP-43. Morphometric analysis showed a 50% decrease in Nf numbers within axons. The decrease in Nf gene expression and Nf numbers was accompanied by a decrease in cross-sectional area and circularity of all myelinated fibers, with the largest fibers showing the most marked changes, and a shrinkage in the perikaryal area of large neurons. Furthermore, we found a concomitant decrease in the expression of transcripts for the nerve growth factor receptors trkA and p75 with aging. Although the mechanisms leading to the decrease in Nf gene expression with aging are not known, a decrease in the availability of growth factors, or the neuron's ability to respond to them, may play a role in this process.

Aging↗
PubMed1994

Relationship between critical thinking skills and success in preclinical courses.

PURPOSE: To examine the relationship between critical thinking skills as measured by the Watson-Glaser Critical Thinking Appraisal (WGCTA) and success during the first two years of medical school. METHOD: The WGCTA was administered to 92 students participating in orientation for the class of 1994. Total scores and subtest scores were calculated for each student. Scores from the Medical College Admission Test (MCAT) subtests, undergraduate grade-point averages (GPAs), gender, race-ethnicity, and other premedical data were obtained from admission files. Measures of student success in medical school included the final numerical scores of preclinical courses, preclinical GPA, United States Medical Licensing Examination (USMLE) Step 1 total score, course remediations, and alterations in schedules such as reduced loads or repeated years. Pearson correlation and the t-test were used in the analysis of data. RESULTS: WGCTA scores correlated best with MCAT scores for reading skils (r = .57) and quantitative skills (r = .40). Significant correlations were found between WGCTA scores and final scores for nearly all preclinical courses; however, the only correlations reaching .40 were for Behavioral Science 1 and Biometrics. Correlations between WGCTA scores and first- and second-year GPAs and scores on the USMLE Step 1 were between .33 and .36. The WGCTA scores for students who had extended time to meet course requirements or altered their curricula were significantly lower than those of students who neither took extended time nor changed their academic schedules. CONCLUSION: Critical thinking skills as measured by the WGCTA are moderately predictive of academic success during the preclinical years of medical education.

College Admission Test↗
PubMed1993

Atrial natriuretic peptide binding in rat placenta, yolk sac, decidua, and maternal placental vessels.

Using in vitro autoradiography, binding sites of 125I-ANP (atrial natriuretic peptide) were localized in the rat placenta, visceral yolk sac, and decidua at 16, 18, and 20 days of gestation. There was diffuse binding over the labyrinthine region of the placenta and an intense binding over the decidual gland and visceral yolk sac. In the yolk sac, ANP localized over the cores of the villi where it may be involved with the regulation of transport across the membranes or the flow of blood through the vitelline vessels. Of particular interest was binding over the maternal blood vessels supplying the decidual region and placenta. Receptors were located on the endothelial cells and smooth muscle cells of the arteries and veins, indicating that ANP may be involved with regional regulation of blood flow to the placenta.

Animals↗
PubMed1991

Immunohistochemical localization of atrial natriuretic peptide in the developing and adult mammalian kidney.

The discovery, within the last decade, of atrial natriuretic peptide (ANP), a family of peptides with natriuretic/diuretic and vasorelaxant properties, has prompted much research into the mechanisms and sites of action of ANP within the kidney. In the present study, ANP was localized in the kidneys of several mammalian species by immunohistochemical techniques 1) to identify possible sites of synthesis; 2) to compare the localization of ANP to known physiological effects; 3) to determine species differences, if any, in ANP localization; and 4) to study the development of ANP immunoreactivity in the fetal and neonatal rat kidney. Using an antibody against rat ANP, IV, ANP was localized exclusively on the proximal convoluted tubule (PCT) brush border and within intercalated cells of the outer medullary and cortical collecting tubules and ducts of adult mouse, rat, pig, monkey, and human kidneys. The development of ANP immunoreactivity paralleled the differentiation and maturation of collecting duct epithelium in rat fetal kidney. Atrial natriuretic peptide found within intercalated cells of the cortical and outer medullary collecting ducts may be the result of endogenous synthesis and, following secretion, may be available to receptors in the inner medullary collecting ducts.

Amino Acid Sequence↗
PubMed1991

Localization of 125I-atrial natriuretic peptide (ANP) in the rat fetus.

In this in vitro autoradiographic study of ANP-binding sites in fetal rats, 125I-ANP bound to receptors in certain developing neural crest derivatives, including the boundary caps, dorsal root ganglia, and Schwann cells of peripheral nerves. Within the spinal cord, ANP receptors were localized in the roof plate and floor plate. The developing meningeal layer of the CNS, blood vessels, lung, liver, and wall of the herniated gut were also labeled. The topographical and temporal correlation of the appearance of ANP receptors with the developmental processes of the targets suggests that ANP in the fetus is multifunctional, and may be involved in diverse events such as gliogenesis, formation of axonal pathways or surfactant production.

Animals↗
PubMed1991

Beta-amyloid precursor protein gene is differentially expressed in axotomized sensory and motor systems.

The beta-amyloid precursor protein (APP) is involved in the degenerative and regenerative neural changes associated with aging and Alzheimer's disease. We studied the regulation of APP gene expression in a paradigm of degeneration and regeneration, the axotomized rat sciatic system. The sciatic nerves of rats were crushed and at intervals between 4 and 60 days, the affected dorsal root ganglia and spinal cord segments were processed for Northern analysis and in situ hybridization to evaluate various APP mRNA species. After nerve crush, dorsal root ganglia APP mRNA levels are increased for both APP695 (695 amino acids) and APPKPI (Kunitz protease inhibitor). Following reinnervation, APP695 returns to baseline but APPKPI remains elevated. In spinal cord there is a decrease of APP695, which returns to baseline following reinnervation. If regeneration is prevented, the initial phase of post-axotomy response for all APP forms persists for at least 60 days in both dorsal root ganglia and spinal cord. In situ hybridization confirms that the changes are referable to neurons. These findings indicate that neuron-target interactions are important in APP gene regulation; that the APP695 and APPKPI transcripts are differentially regulated following neuronal injury; and that different neuronal populations regulate APP expression in a cell-type specific manner.

Amyloid beta-Protein Precursor↗
PubMed1989

Ontogeny of atrial natriuretic peptide receptors in fetal rat kidney and adrenal gland.

With in vitro autoradiography, specific receptors for atrial natriuretic peptide (ANP) were localized in fetal rat kidney and adrenal glands. Receptors were present over renal vesicles, in the primitive renal medulla and throughout the adrenal gland as early as 16 days gestation. By 20 days gestation, several layers of developing renal corpuscles were present and ANP receptors were localized over developing glomeruli in each layer. Larger accumulations occurred over the juxtamedullary glomeruli. In the medulla, the receptors were localized in a reticular pattern near the pelvis. With emulsion coated sections, ANP receptors in developing renal corpuscles were seen primarily over the lower curve of S-shaped vesicles and around the periphery of the more mature corpuscles. In the renal medulla, receptors were localized over the interstitial cells. In the 16-day-old adrenal gland, ANP receptors were present throughout the cortical area but at 20 days gestation and 1 day postpartum receptors appeared more numerous in the peripheral region. These data suggest that ANP has important developmental effects in the kidney and adrenal gland and may be involved in regulation of body fluid homeostasis in the late gestation rat fetus.

Adrenal Glands↗
PubMed1988

Development of immunoreactive atrial natriuretic peptide in fetal hearts of spontaneously hypertensive and Wistar-Kyoto rats.

The development of immunoreactive atrial natriuretic peptide (ANP) was studied in fetal hearts of spontaneously hypertensive (SHR) and compared to normotensive Wistar-Kyoto (WKY) rats. While SHR fetal hearts were noticeably less developed than those of WKY at 10 and 11 days gestation, both strains showed ANP immunoreactive cells in some but not all primitive heart tubes. At 12 days additional ANP immunoreactive cells appeared in formative trabeculae of the ventricle and atrium. ANP cells were also observed in the myogenic layer of the truncus and bulbus arteriosus and their derivatives from 11 through 16 days, but not at 18 days. In both strains, there were more ANP cells in the left ventricle than in right beginning at day 13. There were no obvious strain differences in the developmental pattern and timing of ANP producing cells. However, on the day of birth, staining was reduced in hearts from some WKY newborn pups compared with hearts from SHR newborns and ventricular staining was reduced in both strains when compared to fetal hearts. These observations indicate that ANP is one of the earliest peptide hormones produced and that the predisposition to genetic hypertension does not appear to influence the development of ANP.

Animals↗
PubMed1988

Disability and dependency in elderly people in residential and hospital care.

Physical dependency and mental impairment were assessed in 143 residents of residential accommodation for the elderly and 125 patients in geriatric continuing-care wards in South Belfast. Although dependency, immobility and incontinence were more common in the hospital patients, there was considerable overlap in the disability levels in the two types of care. There was evidence of dementia in 51% of the residents and 71% of the patients, while 29% of residents and 70% of patients were incontinent. Overall, less than 1% of the elderly population was in each of residential or geriatric hospital care but the proportion rose with age and was greater in older women. About 17% of elderly people in South Belfast with dementia were in residential or geriatric hospital care. The projected increase in the number of oldest people, particularly women, and the increased risk of dementia in this age group, means that the need for residential and continuing hospital care for the elderly will continue to increase.

Age Factors↗
PubMed1988

Psychology of computer use: V. Computer use and the experience of time.

To determine whether estimates of duration are altered when people use computers, 60 undergraduates solved easy or difficult single-solution anagrams presented on paper and by computer. Subjects who solved easy anagrams presented on paper underestimated the duration of time allowed for the task, while subjects who completed the anagrams presented by computer overestimated that duration. Also, subjects who solved difficult anagrams presented on computers solved significantly fewer anagrams than did subjects who solved difficult anagrams presented on paper. Results are discussed in terms of contradictory results of past research regarding perceived complexity of events in intervals and the interaction of task type and time estimation.

Data Display↗