Facial expression of affect in children with Cornelia de Lange syndrome

BACKGROUND

Individuals with Cornelia de Lange syndrome (CdLS) have been reported to show comparatively high levels of flat and negative affect but there have been no empirical evaluations. In this study, we use an objective measure of facial expression to compare affect in CdLS with that seen in Cri du Chat syndrome (CDC) and a group of individuals with a mixed aetiology of intellectual disabilities (ID).

METHOD

Observations of three groups of 14 children with CdLS, CDC and mixed aetiology of ID were undertaken when a one-to-one interaction was ongoing.

RESULTS

There was no significant difference between the groups in the duration of positive, negative or flat affect. However, the CdLS group displayed a significantly lower ratio of positive to negative affect than children in the other groups.

DISCUSSION

This difference partially confirms anecdotal observations and could be due to the expression of pain caused by health problems associated with CdLS or neurological expression of the CdLS gene in facial muscles related to expression of positive affect. However, further research is needed to directly test these possible associations.

A cAMP and Ca2+ coincidence detector in support of Ca2+-induced Ca2+ release in mouse pancreatic beta cells

The blood glucose-lowering hormone glucagon-like peptide-1 (GLP-1) stimulates cAMP production, promotes Ca2+ influx, and mobilizes an intracellular source of Ca2+ in pancreatic beta cells. Here we provide evidence that these actions of GLP-1 are functionally related: they reflect a process of Ca2+-induced Ca2+ release (CICR) that requires activation of protein kinase A (PKA) and the Epac family of cAMP-regulated guanine nucleotide exchange factors (cAMPGEFs). In rat insulin-secreting INS-1 cells or mouse beta cells loaded with caged Ca2+ (NP-EGTA), a GLP-1 receptor agonist (exendin-4) is demonstrated to sensitize intracellular Ca2+ release channels to stimulatory effects of cytosolic Ca2+, thereby allowing CICR to be generated by the uncaging of Ca2+ (UV flash photolysis). This sensitizing action of exendin-4 is diminished by an inhibitor of PKA (H-89) or by overexpression of dominant negative Epac. It is reproduced by cell-permeant cAMP analogues that activate PKA (6-Bnz-cAMP) or Epac (8-pCPT-2'-O-Me-cAMP) selectively. Depletion of Ca2+ stores with thapsigargin abolishes CICR, while inhibitors of Ca2+ release channels (ryanodine and heparin) attenuate CICR in an additive manner. Because the uncaging of Ca2+ fails to stimulate CICR in the absence of cAMP-elevating agents, it is concluded that there exists in beta cells a process of second messenger coincidence detection, whereby intracellular Ca2+ release channels (ryanodine receptors, inositol 1,4,5-trisphosphate (IP3) receptors) monitor a simultaneous increase of cAMP and Ca2+ concentrations. We propose that second messenger coincidence detection of this type may explain how GLP-1 interacts with beta cell glucose metabolism to stimulate insulin secretion.

Negative inotropic effect of nifedipine in the immature rabbit heart is due to shortening of the action potential

Contractions in neonatal rabbit ventricular myocytes seem to depend predominantly on Ca2+ influx through the Na+-Ca2+ exchanger (NCX). Unexpectedly, neonates are sensitive to the negative inotropic effect of L-type Ca2+ channel blockers. L-type Ca2+ channel blockers depress contractile function indirectly in neonatal myocytes by shortening the action potential duration (APD), thereby decreasing the influx of activator Ca2+ through the NCX. Freshly isolated ventricular myocytes from adult and neonatal (1-5 d) rabbits were electrically stimulated (0.5 Hz; 35 degrees C) while action potential (AP) and Ca2+ transients (Indo-1) were recorded in the absence and presence of nifedipine (10 microM). In separate experiments, cells were voltage-clamped with a constant AP waveform (APD90=170 ms) to determine the effect of nifedipine on Ca2+ transients independent from effects on the AP. Voltage-clamp experiments confirmed that nifedipine blocks L-type Ca2+ current in neonatal myocytes. Nifedipine markedly reduced Ca2+ transient amplitude and APD in both adults (transient=20 +/- 7%; APD90=31 +/- 4% of control) and neonates (transient=38 +/- 10%; APD90=57 +/- 6% of control). When the AP was held constant by voltage clamping, nifedipine significantly reduced the amplitude of Ca2+ transients in adults (27 +/- 9% of control) but had no effect on Ca2+ transient amplitude in neonatal myocytes. These results are consistent with the concept that immature ventricular myocytes are less reliant on L-type calcium channels and are more dependent on NCX for contraction. The negative inotropic effect of L-type Ca2+ channel blockers in neonates is attributable to shortening of the AP.

Paradoxical Effect of Dofetilide on Action Potential Duration and Calcium Transient Amplitude in Newborn Rabbit Ventricular Myocytes

The Na+-Ca2+ exchanger (NCX) is up-regulated in the neonatal rabbit heart. Because the duration of membrane depolarization is an important determinant of calcium entry via NCX, pharmacological agents that lengthen the action potential (AP) may significantly increase the amount of activator calcium in newborns. We tested this potentially novel therapeutic strategy by using action potential voltage clamp steps or using dofetilide, a blocker of IKr, to prolong the action potential duration (APD). The effects of changing APD on calcium transients were determined in ventricular myocytes at different developmental stages: newborn (1-4 days), juvenile (9-10 days), and adult ventricular myocytes (35 degrees C; 1 Hz). Calcium transient amplitude in neonatal myocytes increased substantially with clamping with longer APs. In contrast, exposure to dofetilide (0.1, 1, and 10 microM) under current clamp conditions increased APD in a concentration-dependent manner but had no significant effect on calcium transient amplitude in either neonates or adults. When the AP was held constant under voltage clamp conditions, dofetilide decreased the calcium transient amplitude in neonates. This effect is likely related to inhibition of sodium-calcium exchanger and L-type Ca2+ currents (ICa), as observed in separate experiments. These results suggest that dofetilide has a paradoxical effect on APD and calcium transients in the newborn heart.

Rapid hyaluronan uptake is associated with enhanced motility: implications for an intracellular mode of action

Texas red-labeled hyaluronan (TR-HA) is rapidly taken up in a CD44 independent manner into ras-transformed 10T1/2 fibroblasts, where it accumulates in both cell ruffles/lamellae, the perinuclear area, and the nucleus. HA does not accumulate in the cell ruffles/lamellae of parental 10T1/2 cells. Addition of HA to ras-transformed cells promotes their random motility but has no effect on 10T1/2 cell motility. 10T1/2 cells can be modified to take up HA into cell ruffles by exposure to phorbol ester or direct microinjection of HA into cells. Both treatments significantly stimulate 10T1/2 cell motility.