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41.
The authors propose and test an exemplar-based random walk model for predicting response times in tasks of speeded, multidimensional perceptual classification. The model combines elements of R. M. Nosofsky's (1986) generalized context model of categorization and G. D. Logan's (1988) instance-based model of automaticity. In the model, exemplars race among one another to be retrieved from memory, with rates determined by their similarity to test items. The retrieved exemplars provide incremental information that enters into a random walk process for making classification decisions. The model predicts correctly effects of within- and between-categories similarity, individual-object familiarity, and extended practice on classification response times. It also builds bridges between the domains of categorization and automaticity. 相似文献
42.
We investigated the fluorescence emission from three fluorophores commonly used for labeling cells in flow cytometry. We have demonstrated that the fluorescence emission from cells labeled with fluorescein-isothiocyanate (FITC), phycoerythrin (PE), and allophycocyanin (APC) is considerably saturated and bleached in standard flow cytometric conditions. Therefore, for optimization of fluorescence detection in a flow cytometer, it is important to know the emission kinetics in detail. We made a mathematical model of the optical processes involved: absorption, fluorescence emission, nonradiative decay, photodestruction, and triplet state occupation. The validity of the model was experimentally tested with a set of averaged fluorescence pulses, measured in a large range of intensities and illumination times. The fluorescence of APC could be completely described by the model and produced the following rate constants: photodestruction rate kb1 = 6 x 10(3) s(-1), triplet state population rate k12 = 2 x 10(5) s(-1), and depopulation rate k20 = 5 x 10(4) s(-1). The fluorescence kinetics of FITC- and PE-labeled cells could not be fitted with only three parameters over the entire range, indicating that other optical processes are involved. We used the model to determine the sensitivity of our flow cytometer and to calculate the optimum conditions for the detection of APC. The results show that in principle a single APC molecule on a cell can be detected in the presence of background, i.e., autofluorescence and Raman scattering by water. 相似文献
43.
ML Uhrig AS Couto MJ Alves W Colli RM de Lederkremer 《Canadian Metallurgical Quarterly》1997,87(1):8-19
Increasingly clinicians attempt to base decisions regarding patient management on the results of clinical studies in addition to expert opinion and their own practical experience. In this article, the author reviews the published studies available to assist clinicians to make evidence-based decisions in three topics related to small volume red blood cell (RBC) transfusions for preterm infants; namely, studies examining the effects of RBC transfusions on possible symptoms of anemia such as tachypnea, apnea or other cardiorespiratory irregularities, studies investigating the collection and transfusion of umbilical cord blood and finally studies addressing the duration of storage and use of additive solutions for RBCs for transfusion to neonates. Based on the review of these studies, guidelines for small volume RBC transfusions in preterm infants are suggested. 相似文献
44.
45.
P Dhordain O Albagli RJ Lin S Ansieau S Quief A Leutz JP Kerckaert RM Evans D Leprince 《Canadian Metallurgical Quarterly》1997,94(20):10762-10767
46.
Evaluation of humoral immune responses in cattle grazing endophyte-infected or endophyte-free fescue
RL Rice DJ Blodgett GG Schurig WS Swecker JP Fontenot VG Allen RM Akers 《Canadian Metallurgical Quarterly》1997,59(3-4):285-291
Anecdotal reports suggest cattle with fescue toxicosis may not respond to vaccination and thus, experience increased incidence of Bovine Respiratory Disease Complex (BRDC) when shipped to feedlots. Fescue toxicosis causes hypoprolactemia in cattle. Hypoprolactemia decreases humoral immune responses in mice. Therefore, a study was conducted to compare the magnitude of primary and secondary humoral immune responses against specific antigens in cattle grazing endophyte-infected or endophyte-free fescue. Angus steers were blocked by weight and allocated into four groups. Two groups grazed endophyte-infected (EI) fescue and the other two groups grazed endophyte-free (EF) fescue. All steers were injected IM on d 0 and 21 with lysozyme without adjuvant and concanavalin. A (Con A) with sheep red blood cells (SRBC) in incomplete adjuvant of Freund. Steers were bled on days 0, 21 and 35 post-vaccination. Average daily gains (ADG), alkaline phosphatase (ALP) activity, cholesterol concentrations, rectal temperatures, and serum prolactin concentrations were measured to confirm fescue toxicosis in steers grazing EI fescue. Antibodies to Con A and SRBC were determined by ELISA and hemagglutination assay, respectively. The ADG were decreased for the EI group during the first month. Rectal temperature were elevated and serum prolactin concentrations were decreased in the EI group. Cholesterol and ALP concentrations also were decreased in the EI group. Primary and secondary immune responses against Con A tended to be increased and were increased against SRBC in the EI group. Antibodies against lysozyme were not induced in either group. In conclusion, cattle grazing EI fescue mounted similar humoral immune responses to vaccination, despite hypoprolactemia, as cattle grazing EF fescue. Increases in bovine respiratory disease in cattle maintained on EI fescue probably is not associated with lack of humoral immune response to vaccination protocols as a result of fescue toxicosis. 相似文献
47.
RM Kaplan 《Canadian Metallurgical Quarterly》1993,86(5):277-281
There is near consensus that the US health care system requires reform. Only a quarter of the American public has faith in the current system. Health care was one of the major issues considered in the 1992 US presidential election and the search for innovative solutions has transcended administrations. 相似文献
48.
Intraneural injection of 10-20 x 10(6) viable Mycobacterium leprae into the sciatic nerve of normal, unsensitized, Swiss white mice gives rise to a tuberculoid type of granulomatous response in 2 weeks. The same dose of viable M. leprae when injected into the sciatic nerves of unsensitized immunosuppressed mice (T200 x 5R) elicited a macrophage response. When macrophages were systemically immobilized using an intraperitoneal injection of silica quartz dust in normal mice, the lesion produced was of the lepromatous type, suggesting a role for the macrophage in the induction of the tuberculoid type of granulomatous response. In all of these in situ experiments, M. leprae failed to enter the Schwann cells. 相似文献
49.
Recurrent hyperparathyroidism due to parathyroid autografts: incidence, presentation, and management
Recurrent hyperparathyroidism (HPT) occurs in a small percentage of patients undergoing parathyroidectomy for primary HPT and is usually due to inadequate excision of hyperfunctioning parathyroid tissue in the neck, a missed ectopic and hyperplastic parathyroid, or, less commonly, parathyroid carcinoma and parathyroid autografts. In order to determine the incidence, clinical characteristics, and outcome of patients with recurrent HPT due to parathyroid autografts, we reviewed our experience with 604 consecutive patients operated on for primary HPT between 1965 and 1989. One hundred of these patients received parathyroid autografts consisting of portions of one or more parathyroid glands. Three patients with autografts, placed in the sternocleidomastoid muscle, developed recurrent HPT due to their autografts for an incidence of 3 per cent. Recurrent disease was diagnosed between 62 and 113 months with an average of 89 months. The autotransplants in all three of these patients were from hyperplastic or adenomatous parathyroid tissue. Two patients had a history of neck irradiation. Preoperative thallium scans accurately localized the hyperfunctioning parathyroid tissue in all three patients. At operation, the hyperfunctioning autografts had grown into a discrete mass with a single vascular pedicle and were resected. Histologic examination disclosed either hyperplastic or adenomatous tissue, and corresponded to the histology and location of the original tissue transplanted in each case. Follow-up ranges from 12 to 67 months, with an average of 48 months. All patients remain cured and none require oral calcium supplementation. We conclude that graft-dependent recurrent HPT is due to the autotransplantation of hyperplastic or adenomatous parathyroid tissue and that thallium scanning is instrumental for diagnosis and localization.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
50.
In this study, rat dermal fibroblasts were used as a model system to examine the ability of ligands that are known to activate protein kinase-C to regulate the levels of the mRNAs encoding basic fibroblast growth factor (bFGF) and insulin-like growth factor-I (IGF-I), two growth factors that are thought to be important in processes such as tissue repair and regeneration and wound healing. Treatment of fibroblasts with the phorbol ester phorbol 12-myristate 13-acetate (PMA), thrombin, bradykinin, serotonin, angiotensin-II, or bombesin increased protein kinase-C activity to a similar degree. Treatment of fibroblasts with 1 microM serotonin transiently increased bFGF mRNA levels about 3-fold compared to the level in control cells maintained in serum-free medium with 0.25% BSA and decreased IGF-I mRNA levels by approximately 50% compared to the level in control cells. This is similar to the previously described changes induced by bradykinin in these cells, but different from the more marked and sustained changes induced by thrombin and PMA. In contrast, angiotensin-II and bombesin had no effect on bFGF or IGF-I mRNA levels. The effects of serotonin, bradykinin, and PMA on bFGF and IGF-I mRNA levels were abrogated by preincubation of cells in 250 nM PMA to down-regulate protein kinase-C. In contrast, the effect of thrombin on bFGF mRNA levels was only partially inhibited by down-regulation of protein kinase-C, while its effect on IGF-I mRNA levels was unaffected. The activation of signaling pathways by the different ligands was further investigated to begin to determine the mechanism for the differences in the effects of thrombin vs. serotonin and bradykinin and in the effects of these three ligands vs. angiotensin-II and bombesin. All of the ligands activated phospholipase-D to a similar degree, suggesting that activation of this enzyme was not responsible for the differential effects of the ligands. In contrast, thrombin, serotonin, and bradykinin had marked effects on the hydrolysis of phosphatidylcholine and phosphatidylinositol, whereas bombesin and angiotensin-II had a small effect on phosphatidylcholine hydrolysis and no effect on phosphatidylinositol hydrolysis.(ABSTRACT TRUNCATED AT 400 WORDS) 相似文献