A new inborn error of glycosylation due to a Cog8 deficiency reveals a critical role for the Cog1-Cog8 interaction in COG complex formation

The hetero-octameric conserved oligomeric Golgi (COG) complex is essential for the structure/function of the Golgi apparatus through regulation of membrane trafficking. Here, we describe a patient with a mild form of a congenital disorder of glycosylation type II (CDG-II), which is caused by a homozygous nonsense mutation in the hCOG8 gene. This leads to a premature stop codon resulting in a truncated Cog8 subunit lacking the 76 C-terminal amino acids. Mass spectrometric analysis of the N- and O-glycan structures identified a mild sialylation deficiency. We showed that the molecular basis of this defect in N- and O-glycosylation is caused by the disruption of the Cog1-Cog8 interaction due to truncation. As a result, Cog1 deficiency accompanies the Cog8 deficiency, preventing assembly of the intact, stable complex and resulting in the appearance of smaller subcomplexes. Moreover, levels of beta1,4-galactosytransferase were significantly reduced. The defects in O-glycosylation could be fully restored by transfecting the patient's fibroblasts with full-length Cog8. The Cog8 defect described here represents a novel type of CDG-II, which we propose to name as CDG-IIh or CDG caused by Cog8 deficiency (CDG-II/Cog8).     

Genomic and phylogenetic analyses of murine adenovirus 2

Murine adenoviruses (MAdV) are supposedly the oldest members of the genus Mastadenovirus. Currently, there are three distinct MAdV types known with rather different tropism and pathology. Here we report and annotate the DNA sequence of the full genome of MAdV-2. It was found to consist of 35,203 bp thus being considerably larger than the genomes of the other two MAdV types. The increased size of the MAdV-2 genome is generally due to larger genes and ORFs, although some differences in the number of ORFs were observed for the early regions E1, E3 and E4. The homologue of the 19K gene of E1B from MAdV-2 codes for 330 amino acids (aa) and is almost twice as large as from other mastadenoviruses. Accordingly, only the N-terminal half (155aa) has homology to the 19K protein. A homologue of the gene of the 12.5K protein was identified in the E3 region of MAdV-2, but not in MAdV-1 or MAdV-3. The other gene of yet unknown function in the E3 region of MAdV-2 seems to be unique. The E4 region of MAdV-2 contains three ORFs. One has similarity to the 34K gene of other AdVs. Two unique ORFs in the E4 region of MAdV-2 have no homology to any of the five and six ORFs in the E4 region of MAdV-1 or MAdV-3, respectively. Phylogenetic analyses showed that the three murine AdVs have a close common ancestor. They likely formed the first branching of the lineage of mastadenoviruses, and seem to be the most ancient representatives of this genus.     

The role of phototherapy in the crash-cart approach to extreme neonatal jaundice

Extreme neonatal jaundice occurs infrequently but carries a high risk of permanent sequelae (kernicterus) when it does. Rapid therapeutic intervention has the potential to reduce this risk in some infants. Several case reports of infants with acute intermediate to advanced bilirubin encephalopathy shows that reversal may be possible. Phototherapy can be instituted at the flip of a switch, whereas other therapeutic measures necessarily involve delays. Therefore, high-intensity phototherapy must be regarded as an emergency measure in infants presenting with extreme jaundice and even more so in the presence of neurological symptoms. The principal and well-described effect of phototherapy involves conversion of bilirubin IXα (z, z) to more polar isomers, which are excreted in bile and urine. When care is taken to maximize the spectral power of phototherapy lights, and whenever possible with measures added to reduce the enterohepatic circulation of bilirubin, very rapid reductions in total serum bilirubin levels are possible. A hypothesis has been advanced that conversion of bilirubin to more polar photoisomers, which can reach relative concentrations of 20%-25% of total serum bilirubin within 1-2 hours, might have a direct neuroprotective effect. This theory posits that because polar molecules generally require a transporter to cross the blood-brain barrier, bilirubin photoisomers should be less prone to enter the brain. Although this theory has some support in in vitro toxicity studies, the evidence is controversial. Until further experimental support can be gained, photoconversion of bilirubin does not constitute a viable argument against instituting further measures against bilirubin neurotoxicity, such as intravenous immune globulin (when indicated) and exchange transfusion. Conversely, neither is the state of evidence an argument against immediate and effective phototherapy in the medical emergency of extreme neonatal jaundice.     

Influence of voltage and extracellular Na+ on amiloride block and transport kinetics of rat epithelial Na+ channel expressed in Xenopus oocytes

We expressed the three subunits of the epithelial amiloride-sensitive Na(+) channel (ENaC) from rat distal colon heterologously in oocytes of Xenopus laevis and analysed blocker-induced fluctuations in current using conventional dual-microelectrode voltage-clamp. To minimize Na(+) accumulation we performed all experiments in low-Na(+) solutions (15 mM). Noise analysis revealed that control or ENaC-injected oocytes did not exhibit spontaneous relaxation noise. However, in ENaC-expressing oocytes, amiloride induced a distinct Lorentzian component in the power density spectra. With three amiloride concentrations and a linear analysis of the respective changes in the corner frequency f(c) (2 pi f(c) plot) we determined the rate constants k(on) and k(off) for the amiloride-ENaC interaction. At a clamp potential (V(m)) of -60 mV k(on) was 80.8 +/- 5.1 microM(-1) s(-1) and k(off) 15.4 +/- 4.2 s(-1). The half-maximal blocker concentration (K(mic,ami)) was 0.19 microM (V(m)=-60 mV). While k(on) was voltage-independent in the range -50 to -100 mV, k(off) and K(mic,ami) decreased significantly with increasing membrane hyperpolarization, resulting in an increased affinity of amiloride for its binding site on ENaC. Increasing extracellular [Na(+)] ([Na(+)](o)) led to saturation of ENaC. Subsequent noise analysis revealed that single-channel current increased non-linearly with [Na(+)](o) and that saturation was not due to a reduction in the number of open channels. The apparent affinity of Na(+) for its binding site on the channel was voltage dependent and increased with hyperpolarization. Noise analysis revealed that k(on) and k(off) for amiloride decreased with increasing [Na(+)](o), while the affinity of the amiloride-binding site did not change. These findings show that the affinity of rat intestinal ENaC for amiloride is voltage dependent and is influenced non-competitively by [Na(+)](o), indicating that Na(+) and amiloride do not compete for the same binding site at the channel.     

Zinc is a voltage-dependent blocker of native and heterologously expressed epithelial Na+ channels

Zn(2+) (1-1,000 microM) applied to the apical side of polarized A6 epithelia inhibits Na(+) transport, as reflected in short-circuit current and conductance measurements. The Menten equilibrium constant for Zn(2+) inhibition was 45 microM. Varying the apical Na(+) concentration, we determined the equilibrium constant of the short-circuit current saturation (34.9 mM) and showed that Zn(2+) inhibition is non-competitive. A similar effect was observed in Xenopus oocytes expressing alphabetagammarENaC (alpha-, beta-, and gamma-subunits of the rat epithelial Na(+) channel) in the concentration range of 1-10 microM Zn(2+), while at 100 microM Zn(2+) exerted a stimulatory effect. The analysis of the voltage dependence of the steady-state conductance revealed that the inhibitory effect of Zn(2+) was due mainly to a direct pore block and not to a change in surface potential. The equivalent gating charge of ENaC, emerging from these data, was 0.79 elementary charges, and was not influenced by Zn(2+). The stimulatory effect of high Zn(2+) concentrations could be reproduced by intra-oocyte injection of Zn(2+) (approximately 10 microM), which had no direct effect on the amiloride-sensitive conductance, but switched the effect of extracellular Zn(2+) from inhibition to activation.     

Cardiac autonomic characteristics in infants sleeping with their head covered by bedclothes

The risk of Sudden Infant Death Syndrome is increased in infants sleeping with their head covered by bedding items. This study was designed to evaluate cardiac autonomic nervous controls in infants sleeping with the head covered by bedclothes. Sixteen healthy infants with a median age of 12 weeks (range 9-13 weeks) were recorded polygraphically for one night. While they slept in their usual supine position, a bedsheet was placed over their head for about 45 min. All infants were challenged with the head covered and with the head free during both rapid eye movement (REM) and non-rapid eye movement (NREM) sleep. Sleep, breathing and heart rate (HR) characteristics were recorded simultaneously, together with rectal and pericephalic temperatures. In both head-free and head-covered conditions, autoregressive spectral analysis of HR was evaluated as a function of sleep stages. During the head-covered periods, parasympathetic tonus decreased and sympathetic activity increased in both REM and NREM sleep. Compared with the head-free periods, the head-covered sleep periods were characterized by greater rectal (P = 0.012) and pericephalic temperatures (P = 0.002). Covering the infant's head with a bedsheet was associated with significant changes in autonomic balance. The finding could be related to an elevation in temperatures within the infant's microenvironment.     

Correlation between liver and plasma fatty acid profile of phospholipids and triglycerides in rats

Considering the changes in the fatty acid profile of liver lipids related to age, gender and nutritional status or occurring in pathological situations, this study aimed at investigating whether such changes could be judged from measurements conducted in plasma lipids. The fatty acid profile of both liver and plasma phospholipids and triglycerides was measured in 16 control animals and 26 rats depleted in long-chain polyunsaturated (n-3) fatty acids. Within each group of rats, significant correlations prevailed between the percentage of each fatty acid in liver versus plasma phospholipids or triglycerides. However, the plasma/liver ratio for the relative content of C20:5(n-3), C22:5(n-3) and C22:6(n-3) in triglycerides displayed abnormally high values in 2 control animals. The fatty acid profile of liver phospholipids and triglycerides can, as a rule, be judged from measurements made in the corresponding plasma lipids. For instance, measurements in plasma phospholipids could help to identify subjects deficient in (n-3) fatty acids and to assess the dietary correction of this defect.     

Fcgamma-receptor IIA genotype and invasive pneumococcal infection

Streptococcus pneumoniae is a major cause of pneumonia, bacteraemia, meningitis, and acute otitis media, especially in young children, immunocompromised patients, and elderly. Fcgamma-IIA receptor plays a crucial role in the phagocytosis of IgG2-opsonized bacteria since it is the sole receptor able to interact with IgG2 antibodies. Fcgamma-RIIA exhibits allelic polymorphisms with different capacities for binding IgG2 and phagocytosis. In a prospective study, we genotyped Fcgamma-RIIA in 55 Caucasian patients suffering from invasive pneumococcal disease and in 100 Caucasian controls. In contrast to previous reports, we found no association between Fcgamma-RIIA genotype and invasive pneumococcal disease.     

Maternal hyperglycemia and adverse pregnancy outcomes in Dar es Salaam,Tanzania

Objective

To evaluate maternal glucose levels during pregnancy as a predictor of adverse perinatal outcomes in Dar es Salaam, Tanzania.

Methods

Random blood glucose measurements were analyzed from 3383 pregnant women enrolled in a randomized trial to assess the impact of multivitamins on pregnancy outcomes in Dar es Salaam between August 2001 and July 2004. Information on maternal and neonatal morbidity was recorded at monthly study visits, delivery, and 6 weeks postpartum. Binomial regression and generalized estimating equations were used to determine the relationship between elevated glucose (> 7.8 mmol/L) and pregnancy outcomes.

Results

In total, 25 women had elevated glucose (0.7%). Hyperglycemia was associated with an increased risk of delivery before 37 weeks [relative risk (RR), 2.11; 95% confidence interval [CI], 1.07–4.13; P = 0.03), delivery before 34 weeks (RR, 4.15; 95% CI, 1.43–12.03, P = 0.009), incident gestational hypertension (RR, 2.90; 95% CI, 1.24–6.76; P = 0.01), low birth weight (RR, 2.87; 95% CI, 1.18–6.99; P = 0.02), reduced newborn head circumference (mean difference, –1.57; 95% CI, –2.51 to − 0.62; P = 0.001), and fetal loss (RR, 3.38; 95% CI, 1.13–10.08; P = 0.03).

Conclusion

Maternal hyperglycemia is uncommon among pregnant Tanzanian women, but nonetheless seems to increase the risk of several adverse perinatal outcomes.