INVESTIGATION ON THE RESPONSE FACTORS OF CONCENTRATION DETECTORS WITHIN SEC PROCESS

The response factors of refractive index (RI) and ultraviolet (UV) detectors of size exclusion chromatography (SEC) defined as the ratio of area of output signal to the mass of injected sample are studied and analyzed by using five narrowly distributed polystyrene (PS) standard samples with known molar masses. It is found that the individual response factor for a given sample varies with the concentration of the injected solution within a limited range bounded by an upper and a lower limiting response factor values. This variation reveals the conformational change of the polymer chains with the concentration of the injected solution. The dynamic contact concentrations cs of the PS samples derived from the response factor data are in good accordance with those reported earlier by other methods. The physical meanings of the signals of the two detectors are further analyzed and theoretically formulated. The solvation of the polymer chain and the conformation changes play an important role in these detecting systems. Both of the solvation number of the structural repeating unit and the extra embedded solvent due to cluster forming in higher concentrations could be deduced from the variation of response factor with the concentration of the injected solution.     

Examining the dimensionality of effortful control in preschool children and its relation to academic and socioemotional indicators.

Effortful control (EC) is an important developmental construct, associated with socioemotional growth, academic performance, and psychopathology. EC is defined as the ability to execute goal-directed behavior to inhibit or delay a prepotent response in favor of a subdominant response. Extant research indicates that EC may be multidimensional. Confirmatory factor analysis with a sample of 234 preschoolers was used to determine if tasks designed to measure EC were best described by hot (affectively salient) and cool (affectively neutral) dimensions or by a single factor. Analyses revealed that EC is best described by a single factor, even when variance associated with children's language skills was removed. This EC factor was strongly related to measures of academic performance and significantly less related to measures of socioemotional development. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Factor VIII inhibitors in mild and moderate-severity haemophilia A

Inhibitors are an uncommon complication of mild haemophilia, occurring in 3-13% of patients and usually arising during adulthood. The risk of inhibitor development in this group appears to be associated with relatively few high-risk factor VIII genotypes clustered in the A2 and C2 domains, especially the Arg593-Cys and the Trp2229-Cys mutations. Kindreds with these mutations have an inhibitor incidence of up to 40%. These mutations may induce a stable conformational change in the factor VIII molecule rendering it antigenically distinct from wild-type factor VIII. Inhibitors in mild haemophilia usually cross-react with endogenous factor VIII reducing the basal VIIIC to < 0.01 IU/ml, and causing spontaneous bleeding. This bleeding is sometimes severe and life-threatening, two-thirds of patients developing a pattern of soft tissue, gastrointestinal (GI) and urinogenital bleeding reminiscent of acquired haemophilia. Bleeding has been treated with human and porcine factor VIII, bypass therapy and DDAVP. Recombinant factor VIIa and DDAVP have the advantage that they do not induce an anamnestic rise in inhibitor titre. About 60% of these inhibitors disappear in the remainder over a median of 9 months. Few of these inhibitors recur, suggesting that most such patients have become tolerant. The inhibitors persist long-term and remain troublesome in about 40% of patients. The limited data available on immune tolerance induction in this group indicate a generally poor response to this approach. Two of nine achieved tolerance, with a partial response in a further four. Inhibitors are an uncommon but life-threatening complication of haemophilia. This complication should be considered when selecting the treatment modality for patients with a family history of inhibitors, and DDAVP used whenever possible.     

Confirmatory factor analysis of items with a dichotomous response format using the multidimensional Rasch model.

Two models that can be used for exploratory factor analysis of items with a dichotomous response format are discussed: threshold models and multidimensional item response models. The models arise from different traditions: The threshold model is rooted in the factor analytic tradition, the multidimensional item response model had its foundation in item response theory. Despite the different origins, it can be proved that both models are the same. Subsequently, the generalized multidimensional Rasch model is introduced. This model can be used for confirmatory factor analysis of items with a dichotomous response format. Stated otherwise, it is the confirmatory counterpart of the (exploratory) threshold and multidimensional item response models. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Proliferative effects of several hematopoietic growth factors on acute myelogenous leukemia cells and correlation with treatment outcome

The response of human acute myelogenous leukemia (AML) cells to four different hematopoietic growth factors (granulocyte-macrophage colony-stimulating factor (GM-CSF), interleukin-1 beta (IL-1beta), interleukin-3 (IL-3), and stem cell factor (SCF)) and the relationship of the proliferative response of the AML cells to treatment outcome were studied. Proliferative responses were analyzed in 79 patients with de novo AML and 19 patients with AML arising from myelodysplastic syndrome (MDS). In de novo AML, a positive proliferative response (stimulation index >2) was seen in 65 to 75% of cases. AML cells arising from MDS had a much higher incidence of proliferative response to each growth factor (79 to 90%) and a much higher level of 3H-TdR incorporation. The relationship to treatment outcome was evaluated in 79 patients with de novo AML. The patients whose leukemic cells had a positive proliferative response to any growth factor, especially IL-3 and SCF, had a poorer outcome, ie a lower complete remission (CR) rate, shorter CR duration, and shorter survival. The outcome was particularly poor in patients whose leukemic cells had proliferative responses to all four or any of the growth factors, compared to patients whose leukemic cells had no response. This increased response may be a marker of poor prognosis in patients with AML.     

Platelet-activating-factor-mediated pathogenesis in Lyme disease

This study describes a role of platelet-activating factor (PAF) as a potential inducer of inflammation in infection with Borrelia burgdorferi. Two approaches were taken. The first involved the use of a PAF antagonist to show the lack of an inflammatory response in skin lesions. The second was to show that the PAF antagonist reduced platelet aggregation when the spirochetes were incubated with polymorphonuclear leukocytes.     

Interleukin-6 downregulates factor XII production by human hepatoma cell line (HepG2)

Involvement of the contact system of coagulation in the pathogenesis of various inflammatory diseases is suggested by reduced plasma levels of factor XII (Hageman factor) and prekallikrein generally considered to result from activation of the contact system. However, in many of these diseases patients develop an acute-phase response and, therefore, an alternative explanation for the decreased levels of factor XII could be the downregulation of factor XII gene expression in the liver as described for negative acute-phase proteins. We report here that interleukin-6 (IL-6), the principal cytokine mediating the synthesis of most acute-phase proteins in the liver, downregulates the production of factor XII by the human hepatoma cell line HepG2 by up to 75%. The decrease in protein secretion correlated with an equivalent decrease of factor XII mRNA likely indicating a pretranslational control of factor XII gene expression by IL-6. Downregulation of factor XII production by IL-6 in vitro parallelled that of transthyretin, a known negative acute-phase protein. Moreover, we show that, in patients developing an acute-phase response after immunotherapy with IL-2, plasma levels of factor XII correlate (r = .76, P < .0001) with those of transthyretin. Taken together, these results suggest that factor XII behaves as a negative acute-phase protein.     

Seminal transforming growth factor beta1 stimulates granulocyte-macrophage colony-stimulating factor production and inflammatory cell recruitment in the murine uterus

Mating in rodents evokes an inflammatory-like reaction within the uterine endometrium, characterized by extensive infiltration and activation of macrophages, dendritic cells, and granulocytes. This response is initiated when seminal vesicle gland-derived factors in the ejaculate stimulate uterine epithelial cells to release proinflammatory cytokines including granulocyte-macrophage colony-stimulating factor (GM-CSF). Experiments in which seminal vesicle secretions were fractionated by Sephacryl S-400 chromatography and assayed in vitro for GM-CSF-stimulating activity revealed that the seminal moiety coeluted with transforming growth factor beta1 (TGFbeta1) in the 150-440-kDa range and was neutralized by anti-TGFbeta1 antibodies. Comparable amounts of recombinant TGFbeta1 stimulated GM-CSF release in cultures of uterine epithelial cells from estrous mice and, when instilled into the uterine lumen, caused an increase in GM-CSF content and an infiltration of leukocytes into the endometrium similar to the postmating response. These results show that seminal vesicular fluid contains TGFbeta1 at levels sufficient to be the primary causative agent in the postmating inflammatory cascade through induction of GM-CSF synthesis by uterine epithelial cells. Seminal TGFbeta1 is thus implicated as a key factor in initiation of the remodeling events and immunological changes that occur in the uterus during the preimplantation period of pregnancy.     

Reduced induction of HSP70 in PC12 cells during neuronal differentiation

Rat pheochromocytoma PC12 cells differentiate into nonreplicating neuronal cells with neurite extensions in response to nerve growth factor (NGF). To gain better understanding of the regulation of stress responses in neuronal cells, we examined the induction of HSP70, HSP70 mRNA, and heat shock factor 1 (HSF1) DNA-binding activity following treatment by heat shock or with sodium arsenite or amino acid analogue in PC12 cells treated with or without NGF. The induction of HSP70 and HSP70 mRNA following these stresses was diminished in the differentiated PC12 cells compared to the undifferentiated cells, whereas the HSF1 DNA-binding activity was enhanced in the differentiated PC12 cells. This phenomenon was characteristic of the differentiated neuronal cells rather than growth-arrested cells. Thus, neuronal cells appear to show an altered stress response depending on their differentiation state, and the diminished HSP70 expression in the differentiated neuronal cells may explain the sensitivity of neuronal cells to pathophysiological stressors.     

Effects of False Floors on Vibration Serviceability of Building Floors. II: Response to Pedestrian Excitation

This is the second of two papers that present the results of a comprehensive and systematic study into the effects of false flooring on the vibration serviceability of long-span concrete floors. In this paper, controlled pedestrian response measurements were utilized to determine the effects of the installation of false flooring on the vibration serviceability of long-span concrete floors. It was found that, in most cases, the installation of false flooring tended to reduce the measured vibration response of the floor under controlled pedestrian excitation. This was more significant for false floors with a relatively high finished floor height (FFH) than for floors with a lower finished floor height. It is tentatively proposed that the effects of false flooring be incorporated into existing design procedures by multiplying calculated responses by a vibration response reduction factor. This factor would be 0.9 for false flooring with FFH less than 500 mm or 0.8 for false flooring with FFH of 500 mm or greater.     

Lipoprotein(a) inhibits lipopolysaccharide-induced tumor necrosis factor alpha production by human mononuclear cells

Lipoproteins can bind lipopolysaccharide (LPS) and decrease LPS-stimulated cytokine production. Lipoprotein(a) [Lp(a)] was as potent as low-density lipoproteins (LDL) in inhibiting LPS-stimulated tumor necrosis factor synthesis by human mononuclear cells. The kinetics of LPS inhibition by Lp(a) was similar to that of LDL. This suggests that circulating Lp(a) may be an important factor determining the amplitude of the response to LPS in humans.     

A glutamate-sensitizing activity in conditioned media derived from rat cerebellar granule cells

When cerebellar granule cells that had been cultured in vitro for 8 days were subjected to a cytotoxic glutamate pulse (100 microM, 30 min incubation), the response varied according to cell density and the volume of medium in which cells were grown. Thus, lowering the cell density by a factor of 4 compared with usual conditions (2.6 x 10(5) cells/cm2) or increasing the volume by an identical 4-fold factor reduced cell death from 90-95% to 20-30%. Addition of a conditioned medium derived from high-density to low-density cultures or to high-volume cultures markedly increased the sensitivity of the cells to glutamate. This glutamate-sensitizing activity, which accelerated by several days the onset of the response of cerebellar cultures to glutamate, was inhibited by actinomycin D and was not detectable in conditioned medium derived from confluent cultures of cerebellar astroglia, or from cell lines such as PC12, GT1-7, 3T3 and CHP 100. Glutamate-sensitizing activity was not mimicked by trilodo-L-thyronine, insulin-like growth factor-I (IGF-I), truncated IGF-I, GPE [a tripeptide (gly-pro-glu) derived from IGF-I], brain-derived neurotrophic factor (BDNF), basic fibroblast growth factor or tumour necrosis factor-alpha. However, IGF-I added to cultures of granule cells plated at high density and grown in basal medium Eagle's without serum or any other constituent of chemically defined media was capable of supporting production of glutamate-sensitizing activity to an extent similar to that shown by whole fetal calf serum. Under the same conditions triiodo-L-thyronine and BDNF did not support the production of glutamate-sensitizing activity. Glutamate-sensitizing activity was not mimicked by glutamate, NMDA, glycine or lactate, and was not inhibited by glucose, haemoglobin or N-omega-nitro-L-arginine methyl ester. At variance with the response of granule cells, the response to glutamate of GABAergic cells present in the same culture was not affected by cell density or by glutamate-sensitizing activity.     

Increased performance using mouthguards--true or false?

High negative middle ear pressure created by habitual sniffing in patients with insufficient closure of the Eustachian tube has been claimed by Magnuson and colleagues to be an important causative factor of acquired cholesteatomas. The present study was conducted to ascertain the rate and types of cholesteatomas in which habitual sniffing is involved. Among 105 consecutive patients with acquired cholesteatomas (112 ears: 93 flaccida type, 15 tensa type, 4 extensive type), 27 patients (31 ears) were diagnosed as having a habitual sniff in response to aural discomfort resulting from insufficient closure of the Eustachian tube. This corresponds to 25.7% of the patients, which is significantly higher than the prevalence of habitual sniffing in normal subjects, being 2 out of 130 (1.5%) (p < 0.005: chi2-test). Habitual sniffing was found to be statistically more common in flaccida-type than in the tensa-type cholesteatomas. Habitual sniffing in response to aural discomfort was thus found to be an important risk factor for cholesteatomas. However, investigations into other pathogeneses of cholesteatomas should be continued, since the sniff-related cases reported here were limited to one-fourth of the cases of acquired cholesteatomas studied.     

Inter-relation of immediate and late asthmatic reactions in childhood

Following bronchial provocation tests with inhalent allergens, late asthmatic reactions (LAR) frequently follow immediate asthma reactions (IAR). This study of atopic asthmatic children demonstrated that patients could show IARs to one allergen, ryegrass extract, but isolated LARs without any preceding immediate response when challenged with an unrelated allergen extract of D. pteronyssinus. The patients' degree of skin sensitivity to the concentration of extract inhaled appeared one factor which determined whether an isolated LAR or IAR followed allergen inhalation.     

Antibiotic resistance pattern and R-plasmids of Acinetobacter calcoaceticus subsp. anitratus

Our objective was to define the maximum tolerated dose of an escalating dose of ifosfamide in combination with a fixed dose of doxorubicin supported by granulocyte colony-stimulating factor (Neupogen). Eighteen women with stage IV breast cancer were enrolled in a Phase I study of an escalating dose of ifosfamide (1.2 g/m2/day for 5 days-2.75 g/m2/day for 5 days) with doxorubicin 20 mg/m2/day for 3 days. Granulocyte colony-stimulating factor was used at 5 microgram/kg on day 6 until hematological recovery. Prophylactic antibiotics were also used. The maximum tolerated dose of ifosfamide in combination with doxorubicin was 2.75 g/m2/day for 5 days. The objective response rate was 83% with a complete response rate of 33% (6/18 patients); the median time to treatment failure was 11.5 months. The median survival has not been reached and will exceed 18 months. We concluded that the recommended dose of ifosfamide in combination with doxorubicin is 2.5 g/m2/day for 5 days. This combination shows promise in stage IV breast cancer.     

Effect of the vascular endothelium on norepinephrine-induced contractions in uterine radial arteries from the nonpregnant and pregnant human uterus

OBJECTIVE: Our purpose was to investigate the role of the endothelium in the human uterine arterial response to norepinephrine in the nonpregnant and pregnant states. STUDY DESIGN: Tissue was obtained from six pregnant and six nonpregnant women undergoing cesarean section or hysterectomy. Uterine radial arteries were isolated and subjected to norepinephrine dose-response curves with and without intact endothelium. RESULTS: Responses were obtained over a dose range of 10(-8) to 10(-4) norepinephrine. Initially there was no difference between vessels from pregnant and nonpregnant patients, but removal of the endothelium significantly increased the response in vessels from pregnant women. Addition of nitro-L-arginine methyl ester when the endothelium was intact did not alter the dose-response curves. CONCLUSIONS: In pregnancy human uterine radial arteries are more sensitive to norepinephrine than during the nonpregnant state. This increase is countered by an endothelium-derived relaxing factor. The factor is unlikely to be nitric oxide.     

Primacy of interresponse-time reinforcement in accounting for rate differences under variable-ratio and variable-interval schedules.

Pigeons' keypeck rates under VR schedules are typically higher than under VI schedules when between-schedule reinforcement rates are equated. Exp I, with 4 male White Carneaux pigeons, reproduced this between-schedule rate difference in a multiple VR-VI schedule. However, when the short interresponse times (IRTs) typically reinforced under VRs were required for VI reinforcement, between-component rate differences diminished. Exp II (4 Ss) replicated Exp I except that long IRTs reinforced under VI schedules were required for VR reinforcement. This manipulation eliminated between-schedule rate differences. In Exp III (4 Ss), VR/VI and VI/VR tandems had the same correlation between response and reinforcement rates. In a simulation, C. P. Shimp's (1969) IRT response rule was used as an algorithm to mimic between-schedule rate difference. Findings show that IRT reinforcement (a molecular factor), rather than the feedback function between response rate and reinforcement rate (a molar factor), accounts for the higher response rates under VR schedules. (25 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)