Comparison of transthecal digital block and traditional digital block for anesthesia of the finger

A randomized, double-blind study was performed in 50 patients to compare the transthecal and traditional subcutaneous infiltration techniques of digital block anesthesia regarding the onset of time to achieve anesthesia and pain during the infiltration. All the patients had sustained injury involving two or four fingers of the hand. Each patient served as his or her own control, having one finger infiltrated with the transthecal technique and the other with the subcutaneous infiltration technique. Time to loss of pinprick sensation and pain (at the time of the infiltration and 24 hours postoperatively) were assessed using a visual analogue scale and verbal response score. A total of 104 blocks (52 transthecal and 52 subcutaneous infiltration) were performed. All of these blocks were successful. Mean time to achieve anesthesia with the transthecal block was 165 seconds, compared with 100 seconds for the subcutaneous infiltration block. The mean analogue pain score was higher for transthecal blocks than for subcutaneous infiltration blocks (3.2 +/- 0.19 versus 1.6 +/- 0.14). Twenty-four hours postoperatively, 24 patients who had the transthecal block experienced pain at the injection site of the digit. However, none of the patients who received the subcutaneous infiltration block complained of pain at the digit. The technique of anesthesia preferred by patients for their finger was the subcutaneous infiltration block, because it causes less pain. Our results confirm the efficacy of the transthecal block for achieving anesthesia of the finger; however, because it is a more painful procedure, it is not recommended.     

Maternal-fetal immune tolerance, block by block

How difficult is to go from egg to implanted embryo? The evolution of placentation in eutherian mammals created enormous challenges, in particular to the maternal immune system, as the fetus expresses paternal antigens that are capable of triggering immune rejection. Samstein et al. reveal a role for inducible regulatory T cells in the enforcement of maternal-fetal immune tolerance.     

Protein-based block copolymers

Advances in genetic engineering have led to the synthesis of protein-based block copolymers with control of chemistry and molecular weight, resulting in unique physical and biological properties. The benefits from incorporating peptide blocks into copolymer designs arise from the fundamental properties of proteins to adopt ordered conformations and to undergo self-assembly, providing control over structure formation at various length scales when compared to conventional block copolymers. This review covers the synthesis, structure, assembly, properties, and applications of protein-based block copolymers.     

Methylation-specific digital karyotyping

Epigenetic alterations, including DNA methylation and histone modifications, are known to regulate various physiological and pathological processes. In mammalian cells, DNA methylation occurs at cytosines of CpG dinucleotides. Several methods have been developed for the genome-wide analysis of methylation patterns. However, none of these are quantitative or sequence-based, and the identification of the exact location of the methylated CpG is difficult. In this protocol, we describe a recently developed method--methylation-specific digital karyotyping (MSDK)--that enables comprehensive and unbiased genome-wide DNA methylation analysis. Using a combination of a methylation-sensitive mapping enzyme (for example, AscI) and a fragmenting enzyme (for example, NlaIII), short sequence tags can be obtained and uniquely mapped to genome location. The number of tags in an MSDK library reflects the methylation status of the mapping enzyme sites. Generation of MSDK libraries can be completed in 7-10 days, whereas sequencing and data analysis requires an additional 3-4 weeks.     

High-speed digital microscopy

High-speed imaging is an ideal technique to accurately resolve the temporal and spatial characteristics of rapid events at either the molecular or cellular level. In this article, the digital imaging techniques used to simultaneously acquire transillumination phase-contrast images, at 240 images s(-1) (high-speed), to characterize ciliary beat frequency, and fluorescence images, at 30 images s(-1) (fast), to measure intracellular calcium concentration ([Ca2+]i), are described. With this technique, a precise correlation between the changes in ciliary beat frequency with changes in [Ca2+]i can be made. Simultaneous imaging is achieved by using different wavelengths of light to form the phase-contrast and fluorescent images and selectively directing these light wavelengths to different cameras with dichroic mirrors and bandpass filters. High-speed images compatible with standard video recording equipment are obtained by prematurely resetting the raster scan of a CCD camera with additional vertical synchronization pulses. The fast [Ca2+]i images are determined using the ratiometric dye fura-2 and a recording technique that monitors rapid changes in fluorescence at a single wavelength and uses intermittent reference images for calibration.     

Megapixel digital PCR

We present a microfluidic 'megapixel' digital PCR device that uses surface tension-based sample partitioning and dehydration control to enable high-fidelity single DNA molecule amplification in 1,000,000 reactors of picoliter volume with densities up to 440,000 reactors cm(-2). This device achieves a dynamic range of 10(7), single-nucleotide-variant detection below one copy per 100,000 wild-type sequences and the discrimination of a 1% difference in chromosome copy number.