Phase transitions in polymer monolayers: Application of the Clapeyron equation to PEO in PPO-PEO Langmuir films

In this paper we investigate the application of the two-dimensional Clapeyron law to polymer monolayers. This is a largely unexplored area of research. The main problems are (1) establishing if equilibrium is reached and (2) if so, identifying and defining phases as functions of the temperature. Once this is validated, the Clapeyron law allows us to obtain the entropy and enthalpy differences between two coexisting phases. In turn, this information can be used to obtain insight into the conformational properties of the films and changes therein. This approach has a wide potential for obtaining additional information on polymer adsorption at interfaces and the structure of their monolayer films. The 2D Clapeyron law was applied emphasizing polyethylene oxide (PEO) in polypropylene oxide (PPO)-PEO block copolymers, based on new well-defined data for their Langmuir films. Values for enthalpy per monomer of 0.12 and 0.23 kT were obtained for the phase transition of two different PEO chains (Neo of 2295 and 409, respectively). This enthalpy was estimated to correspond to 1.2±0.4 kT per EO monomer present in train conformation at the air/water interface.

Barnum Meets the Computer: A Critical Test

The effects of type of assessment device (computer vs. human) on subjects' acceptance of a favorable or unfavorable personality feedback were investigated. Forty-four French-speaking subjects were administered a fictitious personality questionnaire and were asked to evaluate how appropriate the personality feedback was as a description of themselves and people in general. Contrary to predictions, there was no interaction between the type of assessment device and the favorability factors. Two previous findings were nevertheless replicated: (a) in all conditions the favorable description was better accepted than the unfavorable one and, (b) subjects rated the favorable description as being more appropriate for themselves than for people in general.

Three dimensional structure of the seventh transmembrane helical domain of the G-protein receptor, rhodopsin

PURPOSE

The three dimensional structure of a peptide comprising the sequence of the seventh transmembrane segment of the G-protein coupled receptor, rhodopsin, was determined in solution.

METHODS

The sequence of the seventh transmembrane segment of rhodopsin, which contains the NPxxY sequence that is highly conserved among G-protein coupled receptors and lys296 that forms the Schiff base with the retinal, was synthesized by solid phase peptide synthesis. The three dimensional structure was determined in solution by high-resolution nuclear magnetic resonance (NMR).

RESULTS

The structure revealed a helix-break-helix motif for this sequence. Two families of structures were observed which differed in the angle between the two helical segments. The sequence of this transmembrane segment overlapped significantly the sequence of a peptide from the carboxyl terminal of rhodopsin, the structure of which was solved previously. The redundant sequence formed a helix in both peptides. It was therefore possible to superimpose the redundant sequence of both peptides and construct a structure for rhodopsin encompassing residues 291-348.

CONCLUSIONS

This structure reveals locations of the lys296 and the acylation sites of rhodopsin that are consistent with the known biochemistry of this receptor. This segmentation approach to membrane protein structure provides important structural information in the absence of an X-ray crystal structure of rhodopsin. The approach is expected to be useful for other G-protein coupled receptors.

Interferon has no protective effect during acute or persistent reovirus infection of mouse SC1 fibroblasts

Mouse SC1 fibroblasts can support reovirus multiplication although they exhibit a partial resistance to viral-induced cytopathology; a significant percentage of infected SC1 cells can remain viable while becoming persistently infected by the virus. In the present study, the possible role of interferon on the fate of reovirus-infected cells was investigated. Treatment of mouse L fibroblasts with beta-interferon resulted in a reduced viral efficiency of plating while essentially no effect was observed on SC1 cells; the results were similar with the unrelated encephalomyocarditis virus. This suggests that the interferon-regulated pathways are somehow deficient in SC1 cells even though these cells do respond to interferon treatment, as evidenced by an increase in the level of active interferon-inducible protein kinase double-stranded RNA-dependent (PKR) enzyme. Persistently infected SC1 cells constitutively release interferon even though treatment with anti-interferon antiserum suggests that interferon presence is unrelated to maintenance of the persistent state. The possible significance of the correlation between the lack of interferon-induced antiviral effect and relative resistance of SC1 cells to viral-induced cytopathology is briefly discussed.

Two basic motifs of reovirus sigma 3 protein are involved in double-stranded RNA binding

It has been reported that the sigma 3 protein of reovirus can exert an inhibitory effect on the cellular double-stranded RNA (dsRNA) activated protein kinase. Activation of this kinase is thought to be a general mechanism mediating a cellular antiviral response. This enzyme can also be activated upon transfection, resulting in translational inhibition of plasmid-encoded mRNAs. sigma 3 has an affinity for dsRNA postulated to be responsible for antikinase activity. In the present study, site-directed mutagenesis was performed on two basic regions previously suggested as dsRNA-binding motifs and the mutant sigma 3 proteins were then expressed in COS cells. These experiments revealed that both motifs are involved in sigma 3 attachment to RNA. Expression of the mutants lacking RNA-binding capability is stimulated by coexpression of another dsRNA-binding protein, the E3L vaccinia virus protein. These results support a model in which the attachment to dsRNA is directly responsible for the trans-stimulating effect of sigma 3 on expression of cotransfected genes.

Reovirus lambda 1 protein: affinity for double-stranded nucleic acids by a small amino-terminal region of the protein independent from the zinc finger motif

The reovirus lambda 1 protein, a major component of the inner capsid, has been shown to exhibit an affinity for dsRNA in a 'Northwestern' filter-binding assay. In the present study it was demonstrated that the protein can bind dsDNA as well as dsRNA. A bacterial expression system was used to study the protein region able to bind to nucleic acids. The amino-terminal 187 amino acids of lambda 1 were fused to the bacterial maltose-binding protein and shown to be sufficient for binding to nucleic acids. The putative zinc finger present on lambda 1 is not encompassed in this fragment of the protein. Site-directed mutagenesis also indicated that this zinc finger motif is unrelated to binding. In contrast, mutations introduced in a previously suggested nucleotide-binding motif almost completely prevented the binding. These data indicate that the amino-terminal end of lambda 1, encompassing its nucleotide-binding motif, is involved in the affinity of this protein for nucleic acids.

Establishment of persistent reovirus infection in SC1 cells: absence of protein synthesis inhibition and increased level of double-stranded RNA-activated protein kinase

In the present study we report the establishment and characterization of an SC1 cell line persistently infected by reovirus. We observed that a significant percentage of SC1 cells was resistant to cell lysis upon infection with non-defective reovirus stocks. The apparent resistance of SC1 cells to the virus-induced inhibition of protein synthesis is probably an important factor favoring the establishment of such a persistence. The remaining cells, obtained following reovirus infection at a high multiplicity of infection, were kept as a continuous cell line and shown to have normal growth rate. They also released a high titer of virus that did not appear to differ from the original stock in neither infectivity nor genomic pattern. Electron microscopic examination further confirmed the presence of well-developed viral inclusions in the persistently infected cells. These cells were resistant to viral superinfection and exhibited a high constitutive level of the double-stranded RNA-activated protein kinase that might be involved in this resistance. We suggest that this cell line might be an interesting, and possibly more natural system than most previously used cell lines, for the continuing study of virus-host cell interactions during establishment of viral persistence using the much-studied model of reovirus infection.

Protein synthesis in different cell lines infected with orthoreovirus serotype 3: inhibition of host-cell protein synthesis correlates with accelerated viral multiplication and cell killing

In this study, we examined the viral multiplication of human reovirus serotype 3 in mammalian cell lines of different species and tissue origins. All cell lines supported viral multiplication to a similar extent, although the kinetics was significantly different in some of these lines. The appearance of infectious virus was delayed in few cell lines. These cell lines also exhibited a much slower rate of cell killing, and in contrast to the others, did not exhibit an inhibition of the synthesis of host-cell proteins. We conclude that the inhibition correlates with rapid cell killing and viral multiplication, while being unrelated to efficient total viral production.

Further characterization of the ts453 mutant of mammalian orthoreovirus serotype 3 and nucleotide sequence of the mutated S4 gene

The sigma 3 protein of mammalian orthoreoviruses has multiple proven and postulated roles during viral multiplication. In this manuscript we took advantage of the availability of the ts453 thermosensitive mutant, already assigned to the S4 gene encoding sigma 3, to begin the elucidation of the relationship between the two main domains and the different roles of the sigma 3 viral protein. The alteration in the mutant appeared to affect the structural role of the protein. Nucleotide sequence determination indicated an especially significant change close to the zinc finger of the protein. These data suggest that the zinc-binding region might be especially important during the assembly of sigma 3 into the viral capsid.

Short-term memory errors for spoken syllables are affected by the linguistic structure of the syllables

Three experiments on short-term serial memory for spoken syllables are reported. The stimuli were CVC (consonant-vowel-consonant) syllables in Experiment 1, CCVs in Experiment 2, and VCCs in Experiment 3. Analyses of subjects' errors showed that the phonemes within a syllable were not equally free to break apart and recombine. Certain groups of phonemes-the vowel-final consonant group of a CVC, the initial cluster of a CCV, and a vowel-liquid group within a VCC-tended to behave as units. These results are consistent with the view that syllables are coded in terms of an onset (initial consonant or cluster) and a rime (remainder). Errors in short-term memory for spoken syllables are affected by the linguistic structure of the syllables.

[25-Hydroxyvitamin D in children 3 to 6 years old followed at the Service de Protection Maternelle et Infantile]

Serum levels of 25 OH-D, Calcium, Phosphorus and Alkaline phosphatase were measured in 53 children. These children, immigrants for 3/4, 3 to 6 years old, were in good health, and usually followed in a medical advice of PMI in the center of the city. During the month of february, march, april, the half of immigrant children have a serum 25 OH-D deficiency and high alkaline phosphatase, when european children have a normal 25 OH-D level and low alkaline phosphatase. After a stay in their origin country, in september, october, the children come back with a normal 25 OH-D level. Difference between winter and autumn is very significative. The risk factors of a vitamin D deficiency are studied.

[Electrophysiological properties of acute intravenous sotalol in man]

The electrophysiological properties of of 0,6 mg/Kg SOTALOL administered intravenously were studied in 15 subjects aged between 32 and 81 years. The following parameters were recorded: sinus rate (SR), corrected sinus node recovery time (SNRT), sinoatrial conduction time (SACT), PA interval, right atrial effective refractory period (ERP), right atrial functional refractory period (FRP), AH interval at rest, at 100 bpm, Luciani-Wenckebach point (LWP), AV node ERP and FRP, HV interval, His-Purkinje ERP, right ventricular ERP, corrected QT interval. At this dosage, intravenous SOTALOL displays two types of behaviour: --That common to the betablocker drugs: slowing SR by 16%, increasing the AV nodal conduction, increasing the AH interval at rest (5%), at 100 bpm (23%), increasing AV nodal ERP (26%) and FRP (20%), decreasing the LWP (18%). --Other properties: increasing intraatrial PA interval (3%), increasing right atrial ERP (II%), FRP (I7%), increasing right ventricular ERP (8%), increasing His-Purkinje ERP (when measurable) (about 6%), no change in corrected QT interval. At this dosage, SOTALOL exhibits electrophysiological behaviour similar to drugs in Class III (Touboul): those with a "wide electrophysiological spectrum".

[Ventricular tachycardia. A possible complication of intravenous atropine in the coronary patient]

Ventricular tachycardia occurred with chest pain in a 64 year old man with coronary artery disease after an intravenous injection of atropine. The particular feature of this case as compared to the other 8 reported cases is the restoration of sinus rhythm after a passage of accelerated idioventricular rhythm by the administration of oxygen and nitroglycerin. The increased oxygen consumption and myocardial ischaemia due to the tachycardia seem to be the factors responsible for these ventricular arrhythmias. Such cases, though rare, incite caution in the administration of atropine to patients with coronary artery disease.