The immunoregulatory nature of iron. II. Lymphocyte surface marker expression

Previously, we presented preliminary evidence that supported our hypothesis for the immunoregulatory nature of iron [7]. The objective of the present work was to test that hypothesis in greater detail. Our approach was to examine the effect that iron had on the expression of the surface markers on lymphocytes that had been activated by pokeweed mitogen (PWM). The two categories of lymphoid surface molecules were enumerated on those cells; first were those that identify T lymphocytes and second, those that appear on the membrane of T cells following activation. The results, as regards T cell-associated molecules, demonstrated that iron suppresses the expression of the molecules identified by the monoclonal antibodies OKT3 and OKT4. It suppressed expression of the T4 molecule in PWM-activated cells (30.6% +/- 4.5; n = 5) compared with untreated but activated cells (52.2% +/- 2.9; n = 5; P = 1.9 X 10(-3) resulting in a reduced helper:suppressor T cell ratio from 2.2 +/- 0.4 to 1.2 +/- 0.3. With regard to activation-associated lymphocyte markers, iron significantly enhanced expression of the receptor for transferrin as identified by the monoclonal antibody, OKT9. However, it failed to change significantly the expression of three other activation-associated markers, namely, Ia, T10, and the receptor that forms thermostable erythrocyte-rosettes (TE-R) with sheep red blood cells (SRC). We conclude from those results that iron has a differential immunoregulatory influence on the expression of certain lymphocyte surface molecules on actively dividing lymphocytes.     

The myogenic response in isolated rat cerebrovascular arteries: vessel model

We develop an integrated model of isolated rat arterial resistance vessel (RV), which can simulate its major property of myogenic response. The vascular smooth muscle cell is an important component of the wall of this vessel, and serves as a vasomotor organ providing the active tension generation that underlies the myogenic response of the wall to stretch. In the previous study, we focused on the development of a smooth muscle cell model that can mimic the strain-sensing and force-generating features of the myogenic mechanism. In the current model, we embed this cell model in a larger vessel wall configuration, and couple the time course of cellular contractile activation to macroscopic changes in vessel diameter. The integrated model is used to mimic published pressure-vessel diameter data obtained from isolated RVs that are mounted in a hydraulic test apparatus. The model provides biophysically based insights into the myogenic mechanism as it responds to changes in transmural pressure, in the presence and absence of Ca2+ blockers applied to the bathing fluid.It mimics measured data very well and provides a model that is able to link events at subcellular level to macroscopic changes in vessel diameter. The model initiates a mechanistic approach to investigate myogenic response, which has not been taken previously by any other models.     

Estimating the relative frequency of leukodystrophies and recommendations for carrier screening in the era of next‐generation sequencing

Leukodystrophies are a heterogeneous group of heritable disorders characterized by abnormal brain white matter signal on magnetic resonance imaging (MRI) and primary involvement of the cellular components of myelin. Previous estimates suggest the incidence of leukodystrophies as a whole to be 1 in 7,000 individuals, however the frequency of specific diagnoses relative to others has not been described. Next generation sequencing approaches offer the opportunity to redefine our understanding of the relative frequency of different leukodystrophies. We assessed the relative frequency of all 30 leukodystrophies (associated with 55 genes) in more than 49,000 exomes. We identified a relatively high frequency of disorders previously thought of as very rare, including Aicardi Goutières Syndrome, TUBB4A‐related leukodystrophy, Peroxisomal biogenesis disorders, POLR3‐related Leukodystrophy, Vanishing White Matter, and Pelizaeus‐Merzbacher Disease. Despite the relative frequency of these conditions, carrier‐screening laboratories regularly test only 20 of the 55 leukodystrophy‐related genes, and do not test at all, or test only one or a few, genes for some of the higher frequency disorders. Relative frequency of leukodystrophies previously considered very rare suggests these disorders may benefit from expanded carrier screening.     

Responses of calves to acute stress: individual consistency and relations between behavioral and physiological measures

The present study examined the consistency over time of individual differences in behavioral and physiological responsiveness of calves to intuitively alarming test situations as well as the relationships between behavioral and physiological measures. Twenty Holstein Friesian heifer calves were individually subjected to the same series of two behavioral and two hypothalamo-pituitary-adrenocortical (HPA) axis reactivity tests at 3, 13 and 26 weeks of age. Novel environment (open field, OF) and novel object (NO) tests involved measurement of behavioral, plasma cortisol and heart rate responses. Plasma ACTH and/or cortisol response profiles were determined after administration of exogenous CRH and ACTH, respectively, in the HPA axis reactivity tests. Principal component analysis (PCA) was used to condense correlated measures within ages into principal components reflecting independent dimensions underlying the calves' reactivity. Cortisol responses to the OF and NO tests were positively associated with the latency to contact and negatively related to the time spent in contact with the NO. Individual differences in scores of a principal component summarizing this pattern of inter-correlations, as well as differences in separate measures of adrenocortical and behavioral reactivity in the OF and NO tests proved highly consistent over time. The cardiac response to confinement in a start box prior to the OF test was positively associated with the cortisol responses to the OF and NO tests at 26 weeks of age. HPA axis reactivity to ACTH or CRH was unrelated to adrenocortical and behavioral responses to novelty. These findings strongly suggest that the responsiveness of calves was mediated by stable individual characteristics. Correlated adrenocortical and behavioral responses to novelty may reflect underlying fearfulness, defining the individual's susceptibility to the elicitation of fear. Other independent characteristics mediating reactivity may include activity or coping style (related to locomotion) and underlying sociality (associated with vocalization).     

Production and characterization of monoclonal antibodies specific for the murine T cell receptor ζ chain

The T cell receptor (TCR) comprises an antigen-specific β heterodimer non-covalently associated with the CD3 γδε and TCR ζ subunits. Both the CD3 and TCR ζ subunits are proposed to be responsible for the intracellular signal-transduction events. We report here the production of eight monoclonal antibodies (mAbs) that bind in an ELISA assay to a 113 amino acid synthetic peptide corresponding to the cytoplasmic domain of TCR ζ. Western blot analysis of anti-CD8 precipitates of lysates of transfectants expressing chimeric CD8/ζ constructs encoding increasing COOH-terminal truncations of TCR ζ indicates that four of these mAbs recognized the region of TCR ζ chain comprising the last 29 COOH-terminal residues. Thus, this region of TCR ζ may encode an immunodominant epitope. Furthermore, one of these mAbs, G3, is capable of precipitating both non-phosphorylated and tyrosine phosphorylated TCR ζ. The G3 mAb should be useful for elucidiating the structural and signalling characteristics of the TCR ζ chain.     

Neuropsychological Deficit and Academic Performance in Children and Adolescents Following Traumatic Brain Injury

Evaluated the utility of neuropsychological testing in predictingacademic outcome in children 1 year following traumatic braininjury (TBI). Fifty-one schoolage children who were admittedto hospital after TBI were assessed with a battery of neuropsychologicalmeasures at 3 months postinjury. Academic achievement was assessedat 3 and 12 months postinjury. The neuropsychological batteryincluded intelligence testing and measures of memory, learning,and speed of information processing. Academic outcome was assessedin terms of post-TBI changes in reading, spelling, and arithmetic;changes in teacher ratings of school performance; and changein school placement. According to logistic regression analysis,change in placement from regular to special education at 1-yearpost-TBI was predicted by injury severity and by neuropsychologicalperformance at 3 months post-TBI. Findings suggest that neuropsychologicaltesting is useful in identifying children with special educationalneeds subsequent to TBI.     

Dynamics of excitation and inhibition underlying stimulus selectivity in rat somatosensory cortex

Neurons in sensory systems respond to stimuli within their receptive fields, but the magnitude of the response depends on specific stimulus features. In the rodent whisker system, the response magnitude to the deflection of a particular whisker is, in most cells, dependent on the direction of deflection. Here we use in vivo intracellular recordings from thalamorecipient neurons in layers 3 and 4 of the rat barrel cortex to elucidate the dynamics of the synaptic inputs underlying direction selectivity. We show that cells are direction selective despite a broadly tuned excitatory and inhibitory synaptic input. Selectivity emerges from a direction-dependent temporal shift of excitation relative to inhibition. For preferred direction deflections, excitation precedes inhibition, but as the direction diverges from the preferred, this separation decreases. Our results illustrate a mechanism by which the timing of the synaptic inputs, and not their relative peak amplitudes, primarily determine feature selectivity.     

Detecting symptom- and test-coached simulators with the test of memory malingering.

The ability of the Test of Memory Malingering (TOMM; Tombaugh, 1996) to detect feigned-memory impairment was explored. The TOMM was administered to three groups: (a) a control group instructed to perform optimally, (b) a symptom-coached group instructed to feign memory problems after being educated about traumatic brain injury symptomatology, and (c) a test-coached group instructed to feign memory problems after being educated about test-taking strategies to avoid detection. The recommended cutoff scores (Tombaugh, 1996) on Trial 2 and the Retention Trial produced overall classification accuracy rates of 96%, with high levels of sensitivity and specificity. Although the symptom-coached group performed more poorly on the TOMM relative to the test-coached group, the test was equally sensitive in detecting suboptimal effort across the different coaching paradigms.