The membrane affinities of the aliphatic amino acid side chains in an alpha-helical context are independent of membrane immersion depth

Understanding, predicting, and designing the binding of peptides and proteins to bilayers require quantifying the intrinsic propensities of individual amino acid residues to bind membranes as a function of structural context and bilayer depth. A host-guest study was performed using the peptide host named helix5 in order to determine the membrane affinities of the aliphatic side chains both in an alpha-helical context and as a function of bilayer depth. Use of the alpha-helical host with a constrained geometry allowed the placement of guest sites at three different depths in bilayers and minimized secondary structural changes due to guest substitutions. Circular dichroism and electron paramagnetic resonance (EPR) were used to characterize the aqueous and bilayer-bound structures of the peptide variants. EPR was also used to measure the bilayer-water partition constants of the peptide variants, and the Delta DeltaGtr values (relative to Gly) of the aliphatic amino acid side chains were subsequently calculated. Surprisingly, the DeltaDeltaGtr values did not significantly vary as a function of the guest site depth in bilayers. In addition, the Delta DeltaGtr values determined in an alpha-helical context are reduced to approximately two-thirds of Delta DeltaGtr values determined in other studies for the bilayer-water and octanol-water partitioning of amino acid side chains in extended and unstructured hosts. Both the relative reduction in Delta DeltaGtr values in the context of an alpha-helical host and the invariance of Delta DeltaGtr values with respect to bilayer depth are consistent with the membrane affinities of the aliphatic residues being largely determined by the classical hydrophobic effect.     

Benign and malignant esophageal strictures: treatment with a polyurethane-covered retrievable expandable metallic stent

PURPOSE: To evaluate the clinical effectiveness of a polyurethane-covered, retrievable, self-expandable metallic stent and hook catheter in the treatment of esophageal strictures. MATERIALS AND METHODS: Stents were constructed of 0.4-mm stainless steel wire in a cylindric zig-zag configuration of six to nine bends. Four to eight stents were connected in tandem by dipping in a polyurethane solution. A nylon loop was hooked inside to each bend of the proximal portion of the stent and strung with a thread. Under fluoroscopic guidance, 22 stents were placed in 16 patients with a malignant stricture and five patients with a benign stricture. The stent was removed with a hook catheter 2 months after placement in patients with a benign stricture and when complications occurred in patients with a malignant stricture. All patients had dysphagia with ingestion of soft foods or liquids. RESULTS: Stent placement was technically successful and well tolerated in 20 patients. In one patient, the stent was misplaced but relocated successfully. After stent placement, all patients were able to ingest solid and/or soft foods without dysphagia. After stent removal, strictures showed improvement but recurred in two patients. CONCLUSION: Use of polyurethane-covered, retrievable expandable stents seems to be a feasible and effective method of treatment of benign and malignant esophageal strictures.     

REM sleep behaviour disorder: an overview

REM sleep behaviour disorder (RSBD) is a recently described parasomnia characterised by a history of excessive nocturnal motor activity and absence of muscle atonia during REM sleep. Only limited literature is available on this condition. The exact prevalence is unclear, but recent studies suggest it might not be an uncommon condition. The elderly are more often affected and there is a male preponderance. While transient RSBD can be seen after taking certain drugs or during drug withdrawal, the chronic type is usually idiopathic or associated with an underlying degenerative neurological condition. It can result in considerable distress and/or serious injury to the patients or their bed partners. Differential diagnoses include sleep-walking, night terrors, nightmares, nocturnal seizures, obstructive sleep apnoea, post-traumatic stress disorder, dissociative states and nocturnal confusional states. The dramatic response to clonazepam highlights the importance of recognition and appropriate treatment of this sleep disorder.     

Reflective digital optical switch (RDOS) for DWDM optical networkapplications

A novel, high-performance, reflective digital optical switch for use in dense wavelength-division-multiplexed (WDM) network applications is presented. Highly reliable Ti-LiNbO₃ devices show high-speed polarization-independent reflection modulation with 30-dB ON-OFF ratios over a wavelength range from 1520 to 1570 nm     

Complex niches favour rational species

On the whole living things evolve from simpler to more complex forms, though not undirectionally. The evolution of more complex species makes the environment more complex and also makes the evolution of even more complex species possible and more selectable. With the evolution of sentients, species can be classified according to their degree of rationality. A more rational species is one whose behaviour (i.e. of its individual members) is controlled (relatively) more by the reward-penalty system than by the automatic, inflexible, programmed responses. In two reasonable simple models, it is shown that a more complex environment favours the evolution of more rational species. This result partly explains the dramatic speed of evolution based mainly on random mutation and natural selection, a speed doubted by creationists.     

NO/cGMP pathway is involved in exocrine secretion from rat pancreatic acinar cells

OBJECTIVE: To identify factors associated with the initiation of breast-feeding in a predominantly Puerto Rican population living in inner-city Hartford, Conn. DESIGN: Retrospective study of 144 Latino women (mean +/- standard deviation age = 26.3 +/- 5.7 years) with children at least 1 year old but younger than 6 years old (mean +/- standard deviation age = 3.0 +/- 1.2 years) at the time of the survey. Women were recruited from agencies sponsoring health programs for mothers and children. They were interviewed in their homes (69%) or at the Hispanic Health Council, Hartford, Conn (31%). SUBJECTS/SETTING: Low-income Latino women who had at least 1 preschooler at the time of the interview. The women lived in inner-city Hartford, and the overwhelming majority were Puerto Rican and received welfare assistance and food stamps. Seventy-eight percent of the women chose to be interviewed in Spanish; the other 22% were interviewed in English. STATISTICAL ANALYSES: Explanatory variables that related to breast-feeding initiation (P < or = .2) in bivariate chi 2 analyses were entered into a multivariate logistic regression model that was reduced using backward stepwise elimination procedures. RESULTS: Multivariate analyses indicated that breast-feeding the previous child, shorter length of maternal residence in the United States, not receiving prenatal bottle-feeding advice, more recent birth, and higher birth weight were positively associated with breast-feeding initiation. A major reason for choosing not to breast-feed was that women felt socially uncomfortable doing it. APPLICATIONS: Breast-feeding initiation was more likely in Latino women who received prenatal breast-feeding counselling and postpartum support. Mothers of low-birth-weight infants and women breast-feeding for the first time may need additional help. These findings can be used by programs like the Special Supplemental Nutrition Program for Women, Infants, and Children to increase breast-feeding initiation.