Down modulation of MHC surface molecules on B cells by suppressive immune complexes obtained from chronic intestinal schistosomiasis patients

The effect of repeated maximal isometric knee extensions on electromechanical delay (EMD) and associated muscle temperature changes were investigated on seven college aged subjects. The exercise produced a significant reduction in muscle contraction force, rate of force development and muscle conduction velocity, whilst the muscle temperature increased by 2.1 degrees C. The EMD increased from a pre-exercise value of 38.4 (SEM 3.4) ms to 55.7 (SEM 3.4) ms post-exercise. In an attempt to evaluate the effect of muscle temperature on EMD, hot and ice-water bags were placed on the quadriceps muscle to alter muscle temperature. The EMD in isometric maximal knee extension was measured at 38, 36, 34, 32 and 30 degrees C. The results showed that the EMD elongated at muscle temperatures either lower or higher than 36 degrees C. It was speculated that the increased muscle temperature might contribute to 20-25% of the EMD elongation found during the fatiguing intermittent exercise. The information of the effects of muscle temperature on EMD could be useful when evaluating the effects of strenuous exercise, in which a substantial muscle temperature change might occur, on the time delay between myoelectrical activity and force generation.     

Differential scanning calorimetry of phenol–formaldehyde resols

Differential scanning calorimetry was used on a range of synthesized phenol–formaldehyde (PF) resols to discover relationships between formulation parameters or physical properties of resols, and their thermal behavior during cure. The thermograms showed either one or two exothermic reactions. The lower exothermic peak temperature varied between 98 and 129°C with changes in the free formaldehyde content. This exotherm is caused by the addition of free formaldehyde to phenolic rings. The upper exothermic peak temperature varied from 139 to 151°C, with the higher temperatures occurring when the formaldehyde-to-phenol molar ratio was low or the total amount of sodium hydroxide relative to phenol was high. These two factors led to resins which contain a somewhat higher level of unreacted ortho or para aromatic ring positions and no free formaldehyde. Consequently, condensation is probably not solely by the faster self-condensation through hydroxymethyl groups, but also includes the slower condensation of hydroxymethyl groups with unreacted ring positions. Gel times show trends with changes of formulation parameters somewhat similar to trends of the upper exothermic peak temperatures.     

Interferon-gamma and interleukin-4 regulate T cell interleukin-12 responsiveness through the differential modulation of high-affinity interleukin-12 receptor expression

Interferon-gamma (IFN-gamma) and interleukin-4 (IL-4) are mutually antagonistic cytokines that stimulate CD4+ T cells to develop into either Th1 or Th2 cells. One feature of Th2 differentiation in mice is the loss of IL-12-induced Jak2 and Stat4 activation, which is accompanied by the inability to produce IFN-gamma in response to IL-12. In this report, we show that freshly isolated human T cells activated with phytohemagglutinin (PHA) in the presence of IL-4 exhibit a greatly diminished response to IL-12, whereas the IL-12 response of T cells activated with PHA plus IFN-gamma is enhanced. Radiolabeled IL-12 binding studies demonstrate that the impairment of T cell IL-12 responsiveness by IL-4 is associated with the down-regulation of high-affinity IL-12 receptor expression. In contrast, the enhancement of IL-12 responsiveness by IFN-gamma is associated with the upregulation of high-affinity IL-12 receptor expression. Through the use of a newly synthesized neutralizing antibody to the low-affinity IL-12 receptor beta subunit (IL-12Rbeta), we show that neither IL-4 nor IFN-gamma affect the expression of IL-12Rbeta, which we determine to be one of at least two low-affinity subunits required for high-affinity IL-12 binding. These findings suggest that IL-4 and IFN-gamma exert opposite effects on T cell IL-12 responsiveness by differentially modulating the expression of low-affinity IL-12 receptor subunits that are distinct from IL-12Rbeta and required, together with IL-12Rbeta, for high-affinity IL-12 binding and IL-12 responsiveness. This provides a basis for understanding the interplay between different cytokines at the level of cytokine receptor expression, and offers insight into one of the mechanisms governing Th1 and Th2 development.     

Bootstrapping conjectural indicators of vulnerability for schizophrenia: A Reply to Faraone's critique of Watt, Grubb, and Erlenmeyer-Kimling.

Presented is a reply to the article "Validating indicators of vulnerability to schizophrenia: A comment on Watt, Grubb, and Erlenmeyer- Kimling", (1983). Demonstration of statistically significant mean differences between high-risk and normal control children provides little information concerning the validity and clinical utility of conjectural indicators of vulnerability to schizophrenia. Taxometric methods offer a promising approach for preliminary testing of the validity and clinical utility of such indicators. It is not required that the indicators be nearly infallible. Accurate identification of vulnerability is still possible by combining several indicators that are fallible but relatively independent within the vulnerable and nonvulnerable subgroups. Mixed-group validation methods would be preferable to criterion-group methods in some vulnerability studies but they require dependable estimates of the base rates of vulnerability in high-risk and control groups, which are not available in the present instance. Because of the lack of an available criterion measure of vulnerability in high-risk studies, uncertainty about the validity of conjectural indicators is presently unavoidable. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Detecting sex bias in salaries.

Asserts that the difference index proposed by the author (in press) represents the most effective means of assessing sex bias in salaries and is preferable to regression-based indices regardless of the type of available measures of qualifications and salary. The difference index defines sex bias as the difference in mean salary inequities between men and women and emphasizes the necessity of deciding how much relevant differences in qualifications are worth. Unlike the regression indices, if measurement errors are uncorrelated with sex, the difference index is unchanged. This index is also applicable to other employee characteristics and types of inequity. (7 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Justifying the use and increasing the power of a t test for a randomized experiment with a convenience sample.

The standard error in an independent-groups t test is usually derived assuming that individuals are randomly sampled from populations of infinite size. However, t tests are routinely used in randomized experiments with individuals obtained from convenience samples. In such cases, the use of a t test is most often justified by supposing (a) that the convenience sample was a random sample from a hypothetical infinite population and (b) that it is this hypothetical population to which inference is being drawn. It is shown how the use of a t test with a convenience sample can be justified without reference to a hypothetical infinite population and how it may be possible to modify the t test to increase its power for drawing inferences in randomized experiments. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Role of transforming growth factor-beta in the preferential induction of T helper cells of type 1 by staphylococcal enterotoxin B

Stimulation of murine CD4+ T cells with staphylococcal enterotoxin B (SEB) results in the preferential development of T helper (Th) 1 cells [i.e. high interferon (IFN)-gamma and low interleukin (IL)-4, IL-5 and IL-10]; whereas in response to plate-bound anti-CD3 or anti-T cell receptor-alpha beta, Th1 as well as Th2 cells develop. In the present study, we examined the mechanism which is responsible for the selective Th1 development in the SEB system. The addition of IL-4 resulted in a strong development of Th2 cells showing that SEB stimulation can result in Th2 differentiation. Co-stimulation with anti-CD28 was insufficient in this regard. Lack of Th2 development in the SEB system was in part due to the inhibitory effect of endogenously produced transforming growth factor-beta (TGF-beta), because anti-TGF-beta allowed the development of Th2 cells. Similarly, TGF-beta inhibited Th2 development and stimulated Th1 development in the anti-CD3 system. This shift was only partially prevented by also including IL-4 in the cultures. The effects of TGF-beta could only partially be explained by stimulation of IFN-gamma or inhibition of IL-4 as intermediatory cytokines: (1) TGF-beta stimulated Th1 development even in the presence of anti-IL-4 and anti-IFN-gamma, and (2) a strong inhibitory effect of anti-TGF-beta on Th1 development was still observed when anti-IL-4 and IFN-gamma were simultaneously added to the cultures. It is concluded that SEB favors Th1 development by stimulation of TGF-beta production. Inhibition of Th2 development by TGF-beta is due, in part, to inhibition of IL-4 and stimulation of IFN-gamma, and, in part, to a direct effect of TGF-beta on the responding T cells.     

Impairment of mycobacterial immunity in human interleukin-12 receptor deficiency

In humans, interferon gamma (IFN-gamma) receptor deficiency leads to a predisposition to mycobacterial infections and impairs the formation of mature granulomas. Interleukin-12 (IL-12) receptor deficiency was found in otherwise healthy individuals with mycobacterial infections. Mature granulomas were seen, surrounded by T cells and centered with epithelioid and multinucleated giant cells, yet reduced IFN-gamma concentrations were found to be secreted by activated natural killer and T cells. Thus, IL-12-dependent IFN-gamma secretion in humans seems essential in the control of mycobacterial infections, despite the formation of mature granulomas due to IL-12-independent IFN-gamma secretion.     

Rejoinder to Tucker's "Comments on 'Confounding of sources of variation in factor-analytic techniques.' "

Reveals that L. R. Tucker's (see 43:2) 2nd rotated factor confounds variation due to pocket vs. wrist watch preferences and variation due to quality preferences. The factor-analytic variation (FANOVA) model does not assume that stimulus main effects represent fundamental psychological constructs. Nor does it make assumptions regarding the presence or absence of general tendencies or individual differences in the data. It describes these aspects of the data separately. Since Tucker's identities break down in most actual applications, the differences between the models are not oridinarily reduced simply to a matter of preference as to which way the mean responses are to be presented. When the intent is specifically to describe individual differences, the FANOVA analysis is more parsimonious and straightforward than analysis of original measures. (PsycINFO Database Record (c) 2010 APA, all rights reserved)