Electrophysiological Phenotype in Angelman Syndrome Differs Between Genotypes

Background

Angelman syndrome (AS) is a severe neurodevelopmental disorder caused by either disruptions of the gene UBE3A or deletion of chromosome 15 at 15q11-q13, which encompasses UBE3A and several other genes, including GABRB3, GABRA5, GABRG3, encoding gamma-aminobutyric acid type A receptor subunits ($\text{β}$3, $\text{α}$5, $\text{γ}$3). Individuals with deletions are generally more impaired than those with other genotypes, but the underlying pathophysiology remains largely unknown. Here, we used electroencephalography (EEG) to test the hypothesis that genes other than UBE3A located on 15q11-q13 cause differences in pathophysiology between AS genotypes.

Effects of unipolar stimulation on voltage and calcium distributions in the isolated rabbit heart

Background  The effect of electric stimulation on the polarization of cardiac tissue (virtual electrode effect) is well known; the corresponding response of intracellular calcium concentration ([Ca²⁺] _i ) and its dependence on coupling interval between conditioning stimulus (S1) and test stimulus (S2) has yet to be elucidated. Objective  Because uncovering the transmembrane potential (V _m)–[Ca²⁺] _i relationship during an electric shock is imperative for understanding arrhythmia induction and defibrillation, we aimed to study simultaneous V _m and [Ca²⁺] _i responses to strong unipolar stimulation. Methods  We used a dual-camera optical system to image concurrently V _m and [Ca²⁺] _i responses to unipolar stimulation (20 ms ± 20 mA) in Langendorff-perfused rabbit hearts. RH-237 and Rhod-2 fluorescent dyes were used to measure V _m and [Ca²⁺] _i , respectively. The S1–S2 interval ranged from 10 to 170 ms to examine stimulation during the action potential. Results  The [Ca²⁺] _i deflections were less pronounced than changes in V _m for all S1–S2 intervals. For cathodal stimulation, [Ca²⁺] _i at the central virtual cathode region increased with prolongation of S1–S2 interval. For anodal stimulation, [Ca²⁺] _i at the central virtual anode area decreased with shortening of the S1–S2 interval. At very short S1–S2 intervals (10–20 ms), when S2 polarization was superimposed on the S1 action potential upstroke, the [Ca²⁺] _i distribution did not follow V _m and produced a more complex pattern. After S2 termination [Ca²⁺] _i exhibited three outcomes in a manner similar to V _m: non-propagating response, break stimulation, and make stimulation. Conclusions  Changes in the [Ca²⁺] _i distribution correlate with the behavior of the V _m distribution for S1–S2 coupling intervals longer than 20 ms; at shorter intervals S2 creates more heterogeneous [Ca²⁺] _i distribution in comparison with V _m. Stimulation in diastole and at very short coupling intervals caused V _m–[Ca²⁺] _i uncoupling at the regions of positive polarization (virtual cathode). Returned for 1. Revision: 22 January 2008 1. Revision received: 13 May 2008 Returned for 2. Revision: 20 June 2008 2. Revision received: 2 July 2008     

Functional human transcobalamin II isoproteins are secreted by insect cells using the baculovirus expression system

Transcobalamin II (TCII) is a cobalamin (Cbl, vitamin B12)-binding protein in mammalian plasma that facilitates the cellular uptake of the vitamin. To obtain human TCII in sufficient quantity for analytical studies, the complementary DNA (cDNA) encoding TCII was inserted into the plasmid PVL 1393, and the baculovirus expressing TCII was obtained by homologous recombination in Spodoptera frugiperda (SF9) insect cells by cotransfection with the wildtype virus. Under optimized conditions, SF9 cells infected with the recombinant virus secreted 2 to 4 micrograms of TCII per milliliter of culture medium. TCII did not accumulate in the SF9 cells and seemed to be constitutively secreted as observed previously in cultured human endothelial cells. The purified recombinant TCII has the same molecular weight by SDS-PAGE as purified human TCII. The recombinant TCII cross-reacts with an antiserum to native human TCII, binds Cbl and facilitates the uptake of Cbl in eukaryotic cells by binding to the receptor for TCII-Cbl on the plasma membrane of K562 cells. Amino acid sequence analysis of the purified recombinant TCII identified two polypeptides, one identical to the amino acid sequence deduced from the cDNA and a second lacking the first and second N-terminal residues. These sequences are identical to two TCII polypeptides purified from Cohn fraction III of pooled human plasma. The two forms of recombinant TCII have the same isoelectric points as the two predominant isoprotein forms of TCII in human serum. Since the baculovirus construct contains a single cDNA that can encode only one amino acid sequence, the two isoproteins in recombinant TCII must be generated by a mechanism other than allele specific expression. A plausible mechanism for generating isoproteins of nonglycosylated peptides, such as TCII, may be by splicing of the leader peptide at alternative sites.     

Metabotropic glutamate receptor signaling is required for NMDA receptor-dependent ocular dominance plasticity and LTD in visual cortex

A feature of early postnatal neocortical development is a transient peak in signaling via metabotropic glutamate receptor 5 (mGluR5). In visual cortex, this change coincides with increased sensitivity of excitatory synapses to monocular deprivation (MD). However, loss of visual responsiveness after MD occurs via mechanisms revealed by the study of long-term depression (LTD) of synaptic transmission, which in layer 4 is induced by acute activation of NMDA receptors (NMDARs) rather than mGluR5. Here we report that chronic postnatal down-regulation of mGluR5 signaling produces coordinated impairments in both NMDAR-dependent LTD in vitro and ocular dominance plasticity in vivo. The data suggest that ongoing mGluR5 signaling during a critical period of postnatal development establishes the biochemical conditions that are permissive for activity-dependent sculpting of excitatory synapses via the mechanism of NMDAR-dependent LTD.Temporary monocular deprivation (MD) sets in motion synaptic changes in visual cortex that result in impaired vision through the deprived eye. The primary cause of visual impairment is depression of excitatory thalamocortical synaptic transmission in layer 4 of visual cortex (1–3). The study of long-term depression (LTD) of synapses, elicited in vitro by electrical or chemical stimulation, has revealed many of the mechanisms involved in deprived-eye depression (4). In slices of visual cortex, LTD in layer 4 is induced by NMDA receptor (NMDAR) activation and expressed by posttranslational modification and internalization of AMPA receptors (AMPARs) (5, 6). MD induces identical NMDAR-dependent changes in AMPARs, and synaptic depression induced by deprivation in vivo occludes LTD in visual cortex ex vivo (6–8). Manipulations of NMDARs and AMPAR trafficking that interfere with LTD also prevent the effects of MD (7, 9–11).Although NMDAR-dependent LTD is widely expressed in the brain (12, 13), it is now understood that different circuits use different mechanisms for long-term homosynaptic depression (14). For example, in the CA1 region of hippocampus, synaptic activation of either NMDARs or metabotropic glutamate receptor 5 (mGluR5) induces LTD. In both cases, depression is expressed postsynaptically as a reduction in AMPARs, but these forms of LTD are not mutually occluding and have distinct signaling requirements (15). A defining feature of mGluR5-dependent postsynaptic LTD in CA1 is a requirement for the immediate translation of synaptic mRNAs (16). In visual cortex, there is evidence that induction of LTD in layers 2–4 requires NMDAR activation, whereas induction of LTD in layer 6 requires activation of mGluR5 (17, 18).The hypothesis that mGluRs, in addition to NMDARs, play a key role in visual cortical plasticity can be traced back more than 25 y to observations that glutamate-stimulated phosphoinositide turnover, mediated in visual cortex by mGluR5 coupled to phospholipase C, is elevated during the postnatal period of heightened sensitivity to MD (19). Early attempts to test this hypothesis were inconclusive owing to the use of weak and nonselective orthosteric compounds (20–22); however, subsequent experiments did confirm that NMDAR-dependent LTD occurs normally in layers 2/3 of visual cortex in Grm5 knockout mice (23).The idea that mGluR5 is critically involved in visual cortical plasticity in vivo was rekindled with the finding that deprived-eye depression fails to occur in layer 4 of Grm5^+/− mutant mice (24). This finding was unexpected because, as reviewed above, a considerable body of evidence has implicated the mechanism of NMDAR-dependent LTD in deprived-eye depression. In the present study, we reexamined the role of mGluR5 in LTD and ocular dominance plasticity in layer 4, using the Grm5^+/− mouse and a highly specific negative allosteric modulator, 2-chloro-4-((2,5-dimethyl-1-(4-(trifluoromethoxy)phenyl)-1H-imidazol-4-yl)ethynyl)pyridine (CTEP), that has proven suitable for chronic inhibition of mGluR5 (25, 26). Our data show that NMDAR-dependent LTD and deprived-eye depression in layer 4 require mGluR5 signaling during postnatal development.     

Lopinavir protein binding in HIV‐1‐infected pregnant women

Background

Pregnancy may alter protein binding (PB) of highly bound protease inhibitors due to changes in plasma concentrations of albumin and α‐1 acid glycoprotein (AAG). Small changes in PB can greatly impact the fraction of drug unbound (FU) exerting pharmacological effect. We report lopinavir (LPV) PB during third trimester (antepartum, AP) compared to ≥1.7 weeks postpartum (PP) to determine if FU changes compensate for reduced total concentrations reported previously.

Methods

P1026s enrolled women receiving LPV/ritonavir, soft gel capsules 400/100 mg or 533/133 mg twice daily. LPV FU, albumin and AAG were determined AP and PP.

Results

AP/PP samples were available from 29/25 women respectively with all but one woman receiving the same dose AP/PP. LPV FU was increased 18% AP vs. PP (mean 0.96±0.16% AP vs. 0.82±0.21% PP, P=0.001). Mean protein concentrations were reduced AP (AAG=477 mg/L; albumin=3.28 mg/dL) vs. PP (AAG=1007 mg/L; albumin=3.85 mg/dL) (P<0.0001 for each comparison). AAG concentration correlated with LPV binding. Total LPV concentration did not correlate with LPV FU AP or PP. However, higher LPV concentration PP was associated with reduced PB and higher FU after adjustment for AAG.

Conclusions

LPV FU was higher and AAG lower AP vs. PP. The 18% increase in LPV FU AP is smaller than the reduction in total LPV concentration reported previously and is not of sufficient magnitude to eliminate the need for an increased dose during pregnancy.

     

DJ‐1 is a Parkinson's disease susceptibility gene in southern Italy

De Marco EV, Annesi G, Tarantino P, Nicoletti G, Civitelli D, Messina D, Annesi F, Arabia G, Salsone M, Condino F, Novellino F, Provenzano G, Rocca FE, Colica C, Morelli M, Scornaienchi V, Greco V, Giofrè L, Quattrone A. DJ‐1 is a Parkinson's disease susceptibility gene in southern Italy. Mutations in the gene DJ‐1 have been shown to be a rare cause of early‐onset Parkinson's disease (EOPD). Since DJ‐1 mutations have been found in patients with Parkinson's disease (PD) from southern Italy, we aimed to investigate whether polymorphisms within the DJ‐1 gene could represent a risk factor for sporadic PD. First, we genotyped 294 patients with PD and 298 controls coming from southern Italy to assess the distribution of the insertion/deletion (Ins/Del) polymorphism. In a second phase, we identified five single‐nucleotide polymorphisms (SNPs) useful to delimit a region potentially involved and genotyped all patients and controls for these markers. All the markers analyzed were significantly associated with PD at both allelic and genotypic level. The most significant association with the disease was found at the Ins/Del polymorphism (p = 0.0001; adjusted odds ratio (OR ) = 2.05; confidence interval (CI ) = 1.36–3.08). When we considered a three‐marker sliding window, we found a highly significant association between the disease and the haplotypes including markers rs17523802, Ins/Del, and rs3766606 (p = 0.0007) and markers Ins/Del, rs3766606 and rs7517357 (p = 0.0054). Our results indicate that polymorphisms located in a region spanning 3535 bp from the promoter to the intron 2 of the DJ‐1 gene confer risk to sporadic PD in southern Italy.     

Trauma to the forearm with damage to the major arteries]

The authors made an analysis of surgical methods of treatment of 63 patients and long-term results in the period from 1 to 6 years in 23 of them. The restoration of all the injured anatomical structures of the forearm and, in particular, the restoration (suture, autovenous plasty) of the major arteries and primary suture of the injured nerves are thought to be necessary for good results.     

Genotype of the cystic fibrosis population of the Hunter Region of New South Wales

Objective : To determine the genotype of patients attending the cystic fibrosis clinic at John Hunter Hospital, Newcastle, Australia.
Methodology : Seventy-five of the 76 patients attending the clinic over a 6 month period had blood collected for genetic analysis of 17 of the cystic fibrosis (CF) gene mutations.
Results : Sixty-one per cent of the patients were homozygous for the ΔF508 mutation and all except one child had at least one ΔF508 mutation.
Discussion : Nearly 80% of the CF genes were the ΔF508 mutation. This prevalence suggests that the obligatory false negative rate of a newborn screening programme for CF based on a combination of immunoreactive trypsin and the ΔF508 gene may be as low as 4-5%.