Coupled cell-free synthesis, segregation, and core glycosylation of a secretory protein

mRNA from rat mammary glands 13-15 days post partum was translated in a wheat germ cell-free system either in the absence or in the presence of ribosome-denuded membranes prepared from isolated rough microsomes of dog pancreas. Newly synthesized alpha-lactalbumin was identified by immunoprecipitation with a monospecific rabbit antiserum against rat alpha-lactalbumin and was characterized by partial amino-terminal sequence determination and by lectin affinity chromatography. In the absence of membranes a presumably unglycosylated form of alpha-lactalbumin was synthesized that bound neither to concanavalin A-Sepharose nor to Ricinus communis lectin-agarose and that contained an amino-terminal signal peptide region comprising 19 amino acid residues. In the presence of membranes a processed form was synthesized that lacked the signal peptide portion and that had an amino-terminal sequence identical to that of mature alpha-lactalbumin. Furthermore, this processed form was found to be segregated, presumably within the microsomal vesicles, because it was resistant to post-translational proteolysis. It was also found to be glycosylated, and because it bound to concanavalin A-Sepharose, from which it could be eluted specifically by alpha-methyl mannoside, but not to R. communis lectin-agarose, it was presumably core-glycosylated. Processing, segregation, and core glycosylation were observed to proceed only when membranes were present during translation and not when they were added after translation.     

Expert insights: The potential role of the gut microbiome-bile acid-brain axis in the development and progression of Alzheimer's disease and hepatic encephalopathy

Recent epidemiological and molecular studies have linked the disruption of cholesterol homeostasis to increased risk for developing Alzheimer's disease (AD). Emerging evidence also suggests that brain cholesterol accumulation contributes to the progression of hepatic encephalopathy (HE) via bile acid (BA)-mediated effects on the farnesoid X receptor. In this perspective paper, we reviewed several recently published studies that suggested a role for the gut microbiota transformation of BAs as a factor in AD and HE development/progression. We hypothesize that in addition to cholesterol elimination pathways, alteration of the gut microbiota and subsequent changes in both the serum and brain BA profiles are mechanistically involved in the development of both AD and HE, and thus, are a potential target for the prevention and treatment of the two diseases. Our understanding of the microbiome-BAs-brain axis in central nervous system disease is still evolving, and critical questions regarding the emerging links among central, peripheral, and intestinal metabolic failures contributing to brain health and disease during aging have yet to be addressed.     

The echo-transponder electrode catheter: a new method for mapping the left ventricle

The ability to locate catheter position in the left ventricle with respect to endocardial landmarks might enhance the accuracy of ventricular tachycardia mapping. An echo-transponder system (Telectronics, Inc.) was compared with biplane fluoroscopy for left ventricular endocardial mapping. A 6F electrode catheter was modified with the addition of a piezoelectric crystal 5 mm from the tip. This crystal was connected to a transponder that received and transmitted ultrasound, resulting in a discrete artifact on the two-dimensional echocardiographic image corresponding to the position of the catheter tip. Catheters were introduced percutaneously into the left ventricle of nine anesthetized dogs. Two-dimensional echo-transponder and biplane fluoroscopic images were recorded on videotape with the catheter at multiple endocardial sites. Catheter location was marked by delivering radiofrequency current to the distal electrode, creating a small endocardial lesion. Catheter location by echo-transponder and by fluoroscopy were compared with lesion location without knowledge of other data. Location by echo-transponder was 8.7 +/- 5.1 mm from the center of the radiofrequency lesion versus 14 + 7.8 mm by fluoroscopy (n = 15, p = 0.023). Echo-transponder localization is more precise than is biplane fluoroscopy and may enhance the accuracy of left ventricular electrophysiologic mapping.     

Atrial Myxomas Grow Faster Than We Think

The finding of a cardiac myxoma usually implies immediate consequent surgical excision to prevent embolic events. Reports with documented growth rate are therefore very rare, and the actual growth rate remains a controversial issue. We report the growth of a left atrial myxoma in an asymptomatic 65‐year‐old patient with several years of follow up for aortic valve disease. A MEDLINE search with the terms “cardiac myxoma and tumor growth” was performed. The calculated growth rate showed an average growth rate of 0.49 cm/month. These reports suggest that the growth rate of myxomas may be faster than is usually thought. (Echocardiography 2010,27:E128‐E131)     

Substituted aminoalcohol ester analogs of indomethacin with reduced toxic effects

Synthesis and evaluation of five different N,N-disubstituted aminoethanol ester derivatives of indomethacin bearing structural resemblance to the aminoethanol ester class of anticholinergics are reported herein. The anticholinergic activity was incorporated into the intact esters to overcome the gastric toxicity of indomethacin, not only by blocking the acidic functionality but also by decreasing gastric secretions and motility. These derivatives exhibited in vitro stability in buffers of pH 2.0 and 7.4 for 6 h and were readily hydrolyzed by human plasma esterases to liberate the parent drug. All the derivatives were significantly less irritating to the gastric mucosa than the parent drug. Though only two esters showed antiinflammatory activity similar to that of the parent drug at equivalent dose levels, all the esters were equipotent to indomethacin in the mouse acetic acid–induced writhing assay for analgesic action. The present evaluation indicates that the combined pharmacological properties of these ester derivatives may prove useful for design and development of novel gastric sparing antiinflammatory molecules with potentially important therapeutic applications.