A versatile route to edge-specific modifications to pristine graphene by electrophilic aromatic substitution

Electrophilic aromatic substitution produces edge-specific modifications to CVD graphene and graphene nanoplatelets that are suitable for specific attachment of biomolecules.

Optimizing the Mass-Specific Activity of Bilirubin Oxidase Adlayers through Combined Electrochemical Quartz Crystal Microbalance and Dual Polarization Interferometry Analyses

Two surface analysis techniques, dual polarization interferometry (DPI) and analysis by an electrochemical quartz crystal microbalance with dissipation capability (E-QCM-D), were paired to find the deposition conditions that give the highest and most stable electrocatalytic activity per adsorbed mass of enzyme. Layers were formed by adsorption from buffered solutions of bilirubin oxidase from Myrothecium verrucaria at pH 6.0 to planar surfaces, under high enzyme loading (≥1 mg mL(-1)) for contact periods of up to 2 min. Both unmodified and carboxylate-functionalized gold-coated sensors showed that a deposition solution concentration of 10-25 mg mL(-1) gave the highest activity per mass of adsorbed enzyme with an effective catalytic rate constant (k(cat)) of about 60 s(-1). The densification of adsorbed layers observed by DPI correlated with reduced bioactivity observed by parallel E-QCM-D measurements. Postadsorption changes in thickness and density observed by DPI were incorporated into Kelvin-Voigt models of the QCM-D response. The modeled response matched experimental observations when the adlayer viscosity tripled after adsorption.

A pilot prospective study of the vascular repair response following red cell transfusion in critically ill patients

BACKGROUND

Red blood cell transfusion has been associated with adverse outcomes including infection, delayed recovery and increased mortality in some patient populations. Circulating cells that yield endothelial-like vascular progenitor cell (VPC) clusters are correlated with vascular repair and recovery after ischaemic injury. The impact of red cell transfusion on VPC clusters and vascular repair remains uncertain.

STUDY DESIGN

We prospectively enrolled patients admitted to intensive care requiring red cell transfusion and subjects at low likelihood of requiring red cell transfusion. Levels of VPC clusters and plasma levels of angiogenic cytokines were compared. A total of 17 patients were recruited and had blood samples collected at time of enrolment and at 24-48 h, 48-72 h and 1 week following transfusion.

RESULTS

We could not discern differences in the number of VPC clusters between transfused patients (n = 6) and non-transfused subjects (n = 11) at baseline or throughout the study period. VPC cluster levels demonstrated wide variance and were highest at 24-h post-enrolment in the entire cohort. Furthermore, levels of all 16 cytokines analysed were not significantly different between transfused and non-transfused patients and we did not observe a correlation between cytokine concentrations and levels of circulating VPC-cluster forming cells in the overall study population.

CONCLUSIONS

Our data suggest that assessment of vascular repair responses after red blood cell transfusion in critically ill patients is challenging. Although our study did not allow us to discern an influence of red cell transfusion on VPC cluster levels or angiogenic cytokines, new methods evaluating vascular repair mechanisms may be required.

Immunization with a pneumococcal capsular polysaccharide vaccine during pregnancy

The feasibility of preventing invasive pneumococcal infections during the first few months of life by immunization during pregnancy has been investigated. One hundred and fifty Gambian women were immunized with either a 23-valent pneumococcal polysaccharide vaccine or a meningococcal polysaccharide vaccine during the last trimester of pregnancy. Pregnant women showed a good antibody response to five of the six pneumococcal polysaccharides tested (types 1, 3, 5, 6, 14 and 19) but not to type 6 polysaccharide. Mean cord blood/maternal blood IgG antibody ratios varied from 24% (type 1) to 49% (type 3) and differed substantially between individual mother/infant pairs. Pneumococcal antibody levels were higher at birth in infants of women immunized with pneumococcal polysaccharide vaccine than in control infants. However, these antibodies disappeared rapidly during the first few months of life and it is uncertain how much clinical protection against pneumococcal infection maternal immunization would have provided.

Meningococcal antibody titres in infants of women immunised with meningococcal polysaccharide vaccine during pregnancy

Seventy five Gambian women were immunised with a single dose of a group A+group C meningococcal polysaccharide vaccine during the last trimester of pregnancy. IgG antibody titres were measured in mothers and in their infants by an enzyme-linked immunosorbent assay (ELISA). All women had a good response to vaccination and maternal antibodies were high at the time of delivery (23.2 micrograms/ml for group A antibodies and 14.3 micrograms/ml for group C antibodies). However, only a proportion of this antibody crossed the placenta; cord blood:maternal antibody ratios were 30% for group A antibody and 44% for group C antibody, respectively. Considerable variability in cord blood:maternal blood ratios was seen between individuals. This could not be related to age, parity, or ethnic group. Mean group A and group C cord blood:maternal blood ratios were lower in women with serological evidence of syphilis than in seronegative women, and diminished transfer of group A antibody was noted in women with active malarial infection of the placenta. Antibody titres declined rapidly in infants and by the age of 3-4 months these had reached control values. Maternal immunisation may give infants some protection against group A and group C meningococcal disease but only during the first few months of life.

Factors affecting the duration of breast feeding: 2. Early feeding practices and social class

Breast milk intake by babies on the third and the sixth postpartum day was measured by a test-weigh procedure in a group of 47 mothers and babies. Women who gave the largest amount of breast milk to their babies on the third postpartum day continued to breast feed for longer than women who gave smaller amounts. These mothers also suckled most frequently, gave least additional fluid to their babies, and their infants regained their birth weight most rapidly. However, an increased early milk intake and duration of breast feeding were both associated with higher social class. These results suggest that, although practices in the initiation of breast feeding are relevant, factors in the background and environment of the mother are also of fundamental importance. Thus recent emphasis on the importance of breast-feeding practices in the immediate puerperium should not divert attention from the equally important task of establishing the optimum conditions for breast feeding in the home environment of mothers.

How long should a breast feed last?

Patterns of milk flow were studied in 50 mothers who were breast-feeding normal birth-weight babies on days 5-7 of the puerperium by progressive test weighing at 5-min intervals during two consecutive feeds. Compared with a regime in which mothers attempted to feed for 10 X 10 min on alternate breasts, a regime of 5 X 5 X 5 X 5 min increased the amount of milk taken in the first 10 min did not influence the final milk intake of the suckling-induced prolactin release. The wide variation of breast-feeding patterns between mothers was demonstrated in respect of the duration of the feed (mean 17.3 min; S.D. +/- 3.1; range 7-30 min), the initial rate of milk flow (mean 6 g/min; S.D. +/- 4.2, range 1-14 g/min) and the final milk intake (mean 70.9 g; S.D. +/- 20.5, range 42-125 g). The advice to breast-feed for 20 min was in appropriate for the majority of mothers because the nutritive feeding time was 15 min or less in 75% of the feeding episodes. The milk intake correlated with the initial rate of milk flow but not with the duration of the feed, the infant's birth weight, or the time since the last feed. It is suggested that the duration of a breast feed should be determined by the infant's response and not by an arbitrary time schedule.

The relationship between suckling-induced prolactin response and lactogenesis

The PRL response to suckling was studied during the first week of the puerperium. Mean basal levels of PRL showed no significant changing during the first week of the puerperium, but there were progressive rises in both the maximum suckling-induced response and the total area under the response curve, which reached peak values on the fourth day after delivery. Despite large variations between individuals in basal PRL levels (range, 0.3-7.0 U/liter), peak suckling-induced response (range, 0.1-9.9 U/liter), and total response (range, 0.6-63.0 arbitrary units), there was much less variability within individuals between consecutive feeds. Using an electronic balance, 20 patients on days 5 and 6 were classified either as good feeders (greater than 60 g milk/feed) or poor feeders (less than or equal to 60 g milk/feed) on the basis of 2 consecutive test weights. The mean PRL response to suckling in 11 good feeders was no different from that in 9 poor feeders, and there was no significant correlation between milk yield and PRL response. Six patients whose infants were in the special care nursery had lactation initiated and maintained by breast pump for an average of 5.6 days. Although the PRL response to the breast pump was very small, these patients also had satisfactory milk yields (mean, 86 g). Although the presence of PRL is essential for lactation, the data in this paper suggest that there is no close temporal correlation between PRL concentrations and milk yield.