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Biomedical subjects

C Drake

Publications and source records attributed to C Drake.

At least 73 records · Page 4Linked to original sources
PubMed1990

Magnetic resonance imaging of acute occlusive intestinal ischemia.

The mortality of acute superior mesenteric artery occlusion and mesenteric infarction remains high, in part because of the failure to identify the patients with the disorder. A reliable noninvasive diagnostic study may facilitate earlier definitive diagnosis and therapy. Proton magnetic resonance imaging may offer a noninvasive diagnostic alternative. We examined this possibility by using an experimental rabbit model of acute superior mesenteric artery occlusion in this study. Animals were scanned 1 hour after the ischemic insult. Relative intestinal wall signal intensity was increased in experimental (ischemic) animals when compared to sham operated controls on T2-weighted (4.35 +/- 0.5 vs 2.57 +/- 0.31, p less than 0.02) and proton spin density-weighted images (2.1 +/- 0.2 vs 1.4 +/- 0.21, p less than 0.05). Significant increases in image intensity were found on T2-weighted and proton spin density images when compared to control animals. Differences between groups could be further highlighted after the administration of a paramagnetic contrast agent gadolinium diethyltriamine pentacetic acid on T1-weighted images. The data from this preliminary study demonstrate that proton magnetic resonance imaging may be used to discriminate between ischemic and nonischemic small intestine. This noninvasive tool may someday become clinically useful to enhance our diagnostic capabilities when a diagnosis of acute superior mesenteric artery occlusion is being entertained.

Animals↗
PubMed1990

Innovations in emergency medical services systems.

This article roughly follows the chronology of an EMS call and discusses innovations in prehospital care, including epidemiology and prevention; precall management (system status management and flexible response); intervention during the call (emergency medicine dispatch); finding the scene; and communications.

Computers↗
PubMed1989

A psychological pulse train: how young children use this cognitive framework to structure simple rhythms.

This paper examines the reproduction of both regular rhythms and irregular sequences by 5- and 7-year-old children, concentrating on the important role played by their organization around a pulse train. It is shown that: (a) the closer rhythms are to a regular beat the easier they are to reproduce and the greater are the improvements with age; (b) memory capacity is limited by the number of pulses around which the rhythm is organized rather than by the number of elements it contains; (c) all the children's productions contain two interval lengths that are in a ratio close to 1:2 and arranged in preferential sequences which we have called "stereotypes"; (d) arrhythmic sequences can only be reproduced if the intervals undergo a systematic distortion towards regularity. These results are interpreted in relation to a pulse-train hypothesis which states that on hearing a rhythm an "internal clock" or "time base" is evoked around which the rhythm is structured.

Attention↗
PubMed1989

Parental attitudes and practices toward children as pedestrians.

Community programs to reduce the toll from pedestrian injuries in childhood must include parents as a key element. This study, consisting of a survey questionnaire, was undertaken to provide information concerning current parent attitudes and practices that could be used to guide prevention programs. The survey consisted of 2464 questionnaires from parents of children in grades kindergarten to four in a suburban school district. Although 94% of parents did not believe that 5- to 6-year-old children can reliably cross streets alone, one third of parents allowed kindergarten-aged children to cross residential streets alone and first-grade children to walk alone to school. The presence of speeding traffic or the lack of safe places to walk did not influence parents in limiting their children's crossings. Few (17%) parents believed that children should be taught not to cross alone; one half of parents, including 41% of parents of kindergarten-aged children believed that children should be taught to cross busy streets without traffic lights. According to results of the study, parent expectations for their children's pedestrian skills may be inappropriate and may be a fruitful target for injury-prevention programs.

Accidents, Traffic↗
PubMed1987

Actions of calcium ions and a calcium-influx blocker on basal and TRH- and GnRH-stimulated hormone release in patients with pituitary adenomas.

We investigated the influence of calcium ions on the secretion of anterior pituitary hormones basally and in response to exogenous hypothalamic releasing factors in 6 men with pituitary tumors. To this end, concentrations of LH, FSH, TSH, growth hormone and prolactin were measured in blood collected at 10-min intervals basally and during a continuous infusion of combined TRH (2 micrograms/min) and GnRH (1 microgram/min). Study sessions were randomized to iv saline, calcium, or diltiazem infusions or oral diltiazem administration. Our results indicate that in contrast to responses in normal men, iv calcium injections do not suppress circulating prolactin concentrations in patients with prolactin-secreting pituitary tumors. Moreover, neither oral diltiazem administration for one week nor acute iv diltiazem infusion suppressed the hyperprolactinemia of tumor patients. However, there were significant effects of drug and calcium treatments on serum concentrations of FSH, GH and testosterone, but not LH or TSH. Moreover, during GnRH-TRH stimulation, there were significant differences in LH, TSH, and testosterone responses in tumor patients compared to normal men. In summary, iv calcium infusion was associated with invariant basal release of anterior pituitary tumoral hormones in patients with pituitary adenomas. However, there were significant differences in the GnRH/TRH-stimulated release of certain anterior pituitary hormones in tumor patients compared to normal men in response to iv calcium and the calcium-channel antagonist, diltiazem.

Adenoma↗
PubMed1987

The migration of myogenic cells from the somites at the wing level in avian embryos.

This study is concerned with establishing a morphological basis for the initiation of migration of putative myogenic cells from the somites into the presumptive wing bud in avian embryos. At the 22 somite stage (stage 14) vasculogenesis is a prevalent activity. By use of a quail specific monoclonal antibody to vascular endothelial cells, vascular cells are recognized in the lateral plate, on the intermediate mesoderm, and on somite surfaces. Cells that are found between the lateral plate mesoderm and somites are shown to be vascular endothelial cells. The lateral body folds progressively bring the lateral plate mesoderm close to the lateral margin of the somites and vascular elements disappear from surface view. It is not until the 24 somite stage (stage 15) that some cells in the ventral lateral margin of somites at the wing level can be seen in scanning electron micrographs to extend basal cell processes toward adjacent vascular tubes. These results provide a morphological basis for the early migratory behavior of myogenic cells and demonstrate their close proximity to the prepatterned vascular network.

Animals↗
PubMed1984

SEM localization of laminin on the basement membrane of the chick corneal epithelium with immunolatex microspheres.

Embryonic chick corneal explants were soaked in mild detergent and the anterior corneal epithelium was peeled from its basement membrane, leaving the lamina lucida surface exposed and supported on the subjacent primary stroma. Explants were treated with rabbit anti-laminin IgG, followed by sheep anti-rabbit IgG linked microspheres, and processed for SEM. The lucida surface was heavily decorated with microspheres, whereas controls treated with preimmune rabbit IgG were essentially beadless. Laminin distribution was not regular, appearing denser in some regions than others. However, the connective tissue surface of the basement membrane was never laminin-positive, even after treatment with hyaluronidase. These results suggest the basal lamina of the corneal epithelium is asymmetric, with preferential location of laminin to the lucida surface of the basement membrane.

Animals↗
PubMed1984

Impaired motor timing control in specific reading retardation.

The temporal organizations of unimanual and coordinated bimanual finger tapping was compared between adolescent normal and retarded readers of above average intelligence. The same subjects were examined for speech articulation during the timed repetition of single syllables and syllable sequences. Retarded readers had substantially greater difficulty on tasks of interlimb coordination than on unimanual tapping and substantially greater difficulty rapidly sequencing syllable strings than repeating single syllables. An experimental manipulation of movement speed for both tasks indicated that the threshold at which movement speed degrades timing precision for coordinated action best characterizes the motor impairment of retarded readers.

Adolescent↗
PubMed1984

SEM localization of cell-surface-associated fibronectin in the cranium of chick embryos utilizing immunolatex microspheres.

Fibronectin has been localized to basement membranes and cell surfaces with the light microscope by fluorescent staining of thick sections, and with the TEM by immunoperoxidase reaction. However, these methods are limited because it is difficult to appreciate the patterned distribution of fibronectin from sectioned material. We have developed a probe for fibronectin that facilitates its identification with the SEM. Our probe consists of two parts; the first component is a derivatized methacrylate microsphere 90 nm in diameter, linked to purified sheep anti-rabbit IgG. The second component is anti-fibronectin IgG raised in rabbits. Stage-3 to -12 chick embryos were fixed and the ectoderm covering the cranial mesoderm was removed. Embryos were treated with testicular hyaluronidase, exposed to rabbit anti-fibronectin IgG and finally to sheep anti-rabbit IgG conjugated microspheres. As expected, the basal lamina of surface and neural ectoderm as well as the remaining fibrous ECM were heavily decorated with microspheres, whereas control embryos treated with preimmune serum were beadless. Fibronectin was localized on the cell soma and processes of primary mesenchyme as early as stage 3. In addition, it was possible to decorate to various extents, populations of prosencephalic, mesencephalic, and rhombencephalic cranial neural crest cells. Our studies suggest that fibronectin is present in the cranium of chick embryos at earlier times than heretofore realized, and that fibronectin accumulates in a cranial to caudal gradient that reflects the sequential differentiation of the embryonic axis.

Animals↗
PubMed1983

Differentiation of praxis among children.

This study was designed to evaluate the conceptual model proposed by Luria to identify different types of dyspraxia in learning-disabled (LD) children. The types of apraxia investigated were kinesthetic, optic-spatial, symbolic, and dynamic. In addition, the study explored differential performance on tasks of praxis in learning-disabled children as a function of their Wechsler Intelligence Scale for Children-Revised (WISC-R) IQ patterns. The subjects included 41 LD and 17 normal children ages 108 months to 153 months. They were administered The Praxis Test for Children, a compilation based on Luria's division of types of praxis with brain-damaged adults. Results indicated that the test differentiated between the LD and normal groups on the dynamic and optic-spatial tests. Data analyzed for the LD children with a significant WISC-R discrepancy between their Verbal IQ and Performance IQ profile yielded no difference between these two IQ groups. Results were discussed in terms of the need to investigate individual patterns of performance in the differentiation of dyspraxia.

Apraxias↗
PubMed1982

Development of a latex-conjugated immunocytological marker for scanning electron microscopic analysis of quail-chick chimeras.

Quail-chick chimeras are created by transplanting pieces of quail tissue to chick. We have used antibodies combined with a cell surface marking technique [modified after Molday et al.('75)], to facilitate scanning electron microscopic (SEM) identification of quail cells in such chimeras. First, antibodies to quail RBCs were raised in rabbits by intravenous injection. Rabbit anti-quail RBC serum was precipitated by ammonium sulfate, purified by DEAE chromatography, and cross-absorbed with chicken RBCs. Second, sheep anti-rabbit IgG was purchased commercially and further purified by affinity chromatography. Third, 900-A-diameter latex beads were synthesized by aqueous emulsion copolymerization of methacrylates. Spheres were bound with diaminoheptane to create an extension arm which was further derivatized in a two-step glutaraldehyde procedure. Purified sheep IgG was bound to the aldehyde-activated spheres, with uncoupled sheep IgG removed by sucrose density centrifugation. To test the marker, rabbit anti-quail IgG was added to 1% diluted quail RBCs. After washing, sheep anti-rabbit IgG bound spheres were introduced. Washed cells were fixed in one-half strength Karnovsky's and processed for SEM. Quail RBCs were uniformly decorated with beads, containing 2,000 beads per cell. Similarly treated chick RBCs show no binding to beads. Likewise, quail RBCs not pre-treated with the rabbit IgG do not bind beads. Prefixed quail RBCs still bind latex-conjugated beads, although at somewhat reduced levels. When mixtures of quail and chick RBCs were processed for identification: (1) sphere labeling was an "all or none" phenomenon; (2) the proportion of bead-decorated cells observable in the SEM was the same as the proportion of quail RBCs provided in the initial mix; and (3) morphologically distinguishable embryonic chick RBCs did not label whereas under the same conditions, quail RBCs do. We further demonstrate that rabbit antibodies prepared by injection of stage 4 quail primitive streaks can be used to specifically label quail epiblast and mesoblast cells, providing markers for at least two germ layers. It is now possible to combine grafting techniques of known success, with SEM analysis of the chimera.

Animals↗
PubMed1982

Screening for specific learning disabilities among dental students.

At a time when recognition of the needs of handicapped students is of great concern, many handicapped persons have not yet been identified. Even with the advent of legislation mandating educational equity for all handicapped students, those with specific learning disabilities (SLD) still remain unidentified or unserved by institutions of higher education. In 1979, New York University College of Dentistry instituted a classwide screening and testing program for SLD students. The program sought to identify accepted students "at risk" for SLD through the administration of a two-hour battery of tests designed by learning disabilities specialists. Follow-up in-depth evaluations yielded a 90 percent accuracy rate on correct identification of SLD students based on the screening results. This article presents specific test results, analyses of data, and comparison of self-report measures and suggests educational implications, including suggestions for program accommodations.

Adult↗
PubMed1981

Bimanual co-ordination in adolescent boys with reading retardation.

The temporal organization of unimanual and bimanual rhythmic finger-tapping was compared between adolescent normal readers and retarded readers, as well as across subgroups of retarded readers with different psychometric intelligence profiles. Regardless of subtype, the retarded readers had substantially greater difficulty in maintaining a steady tapping rhythm than did controls, but their deficit was limited to motor tasks requiring asymmetrical timing commands to the two hands. The findings indicate that the motor deficits of retarded readers on complex skills persist into adolescence; and they suggest that one major source of difficulties in motor performance may be in rapid communication between the hemispheres.

Adolescent↗