Helicases and RNA unwinding in translation: Current opinion in structural biology 1993, 3: 953–959

RNA helicases melt regions of duplex RNA in a process that requires energy derived from the hydrolysis of nucleoside triphosphates. The process of protein synthesis in prokaryotes and eukaryotes involves one proven RNA helicase (elF-4A) and several putative RNA helicases. Of these, one group of helicases is thought to unwind secondary structure in the 5′ non-coding region of mRNAs to facilitate ribosome binding. A second group is implicated in ribosome assembly, in particular in ribosomal RNA maturation.     

Infectivity,viability and effects of Paranosema locustae (Microsporidia) on juveniles of Dichroplus maculipennis (Orthoptera: Acrididae: Melanoplinae) under laboratory conditions

Infectivity and effects on host of a long-term stored aqueous suspension of Paranosema locustae on juveniles of Dichroplus maculipennis, a pest grasshopper in parts of the Pampas and Patagonia, were evaluated. Infections developed in 90–97.8% of treated individuals. Mortality increased with time, reaching highest values at 30–40 days post-inoculation (79.5–100%). Infected nymphs showed significantly slower development.     

Pressure, flow, and density relationships in airway models during constant-flow ventilation

Adequate CO2 elimination and normal arterial PCO2 levels can be maintained in dogs during apnea by delivering a continuous flow of inspired gas at high flow rate (1-3 l.min-1.kg-1) through tubes placed in the main-stem bronchi. However, during constant-flow ventilation (CFV) the mean alveolar pressure is increased, causing increased lung volume despite low pressures in the trachea. We hypothesized that the increased dynamic alveolar pressures during CFV were due to momentum transfer from the high-velocity jet stream to resident gas in the lung. To test this, we simulated CFV in straight tubes and in a branched airway model to determine whether changes in gas flow rate (V), gas density (rho), and tube diameter (D) altered the pressure difference (delta P) between alveoli and airway opening in a manner consistent with that predicted by conservation of momentum. Momentum analysis predicts that delta P should vary with V2, whereas measurements yielded a dependence of V1.69 in branched tubes and V1.9 in straight tubes. Substitution of heliox (80% He-20% O2) for air significantly reduced lung hyperinflation during CFV. As predicted by momentum transfer, delta P varied with rho 1.0. Momentum analysis also predicts that delta P should vary with D-2.0, whereas measurements indicated a dependence on D-2.02. The influence of V and rho on depth of penetration of the jet down the airway was explored in a straight tube model by varying the flow rate and gas used. The influence of geometry on penetration was measured by changing the ratio of jet-to-airway tube diameters.(ABSTRACT TRUNCATED AT 250 WORDS)     

Synaptonemal complexes and chromosome chains in the rodent Ellobius talpinus heterozygous for ten Robertsonian translocations

Synaptonemal complexes (SC) in four Ellobius talpinus males heterozygous for ten Robertsonian translocations were examined with an electron microscope using a surface-spreading technique. A total of 136 late zygotene and pachytene spermatocytes were examined. From one to three completely paired SC trivalents were found in each early pachytene spermatocyte. The lateral elements of the short arms of the acrocentric chromosomes in these trivalents were joined with an SC thus forming the third arm of the SC trivalent. At the same stage a few SC trivalents did not contain lateral elements in the pericentromeric region of the metacentric chromosomes and remained unpaired in this region up to mid pachytene. At zygotene and pachytene from two to eight SC trivalents were joined into chains due to formation of SCs between the short arms of acrocentrics of other SC trivalents. These chains are frequent at late zygotene, but are resolved during pachytene into individual trivalents. It is proposed that pairing and SC formation between the short arms of the acrocentric chromosomes results from the monosomy of the short arms and partial DNA homology between these heterochromatic regions. Since crossing over probably does not take place in these segments, the chromosomal chains may subsequently be corrected into trivalents by a dissolution of the SCs combining adjacent trivalents. The correction and disjoining of chains may not be effective in all cells. The cells in which the chains are retained are assumed to be arrested at the pachytene stage.     

Fluorescent and Ferritin Labelling of Cuticle Surface Carbohydrates of Caenorhabditis elegans and Panagrellus redivivus

Caenorhabditis elegans and Panagrellus redivivus were investigated for surface carbohydrates using fluorescent-labelled and ferritin-labelled lectins. Rhodamine-labelled Concanavalin A was specifically located in the cephalic region of both species. Rhodamine-labelled wheat germ agglutinin was located over the entire cuticle of P. redivivus but was absent on C. elegans. Rhodamine-labelled peanut agglutinin and Limax flavus agglutinin did not label nematodes of either species. Galactose and sialic acid were not detected on either species, whereas mannose-glucose residues were specifically localized in the head areas of both species. No detectable N-acetylglucosamine occurred on C. elegans, but it was evenly distributed over the cuticle surface of P. redivivus.     

Oxyphenbutazone (Tandearil?) in Rhinoplasty—A Clinical Evaluation of Effectiveness

To evaluate the effectiveness of Oxyphenbutazone as an anti-inflammatory agent, a double-blind study of Oxyphenbutazone and a placebo in a group of 42 patients who had nasal cosmetic operations involving osteotomy was carried out. The observations included direct objective measurement of the width of the palpebral fissure after operation, grading of the severity of postoperative edema and ecchymosis from photographs, and observations by the patients regarding the clearing of the postoperative discoloration. It appeared from the results of these observations that Oxyphenbutazone is not effective in preventing postoperative edema in such operations or in promoting more rapid resolution of postoperative edema. It did appear to enhance the clearing of postoperative periorbital ecchymosis.     

Measurement of hydrogen peroxide in plasma and blood

Measurement of the oxygen metabolite hydrogen peroxide (H2O2) in biological fluids such as plasma could be of interest because it might indicate participation of toxic oxygen species in tissue injury. Recently several reports claimed to measure H2O2 using spectrophotometric and high pressure liquid chromatographic (HPLC) techniques that utilize oxidation of a substrate to a product by a peroxidase. In such a system it is crucial to perform two control experiments to verify whether the measured substance is H2O2. The specificity of the assay for H2O2 should be checked with catalase, and the degradation of H2O2 or inhibition of the assay system by the sample should be checked by determining the recovery of exogenously added H2O2. We performed both types of controls for HPLC and spectrophotometric determinations of H2O2 in plasma and blood. Our results indicate that contrary to previous reports in the literature the measured substance(s) in plasma or blood is not H2O2. Moreover, quantitative measurements of H2O2 in plasma or blood by HPLC was unreliable due to the irreversible binding of H2O2 to the column surface.     

Complete sequence of a new HLA-B35 allele found in a tribe of Mapuche Indians in the south of Argentina

The nucleotide sequence data reported in this paper have been submitted to the GenBank nucleotide sequence database and have been assigned the accession number U17107. The nameB*3509 was officially assigned by the WHO Nomenclature Committee in December 1994     

Murine p53 inhibits the function but not the formation of SV40 T antigen hexamers and stimulates T antigen RNA helicase activity

We have characterized the effects of p53 on several biochemical activities of simian virus 40 (SV40) large tumor (T) antigen. While p53 induced a strong inhibition of the T antigen DNA helicase activity, surprisingly, its RNA helicase activity was stimulated. This supports the liklihood that the DNA and RNA helicase activities of T antigen reflect discrete functions. p53 did not significantly affect the ATP-dependent conversion of T antigen monomers to hexamers. However, the ability of these hexamers to assemble on a DNA fragment containing the viral origin was impaired by p53. Thus, these results suggest that p53 inhibits the function but not the formation of T antigen multimers. This conclusion was further supported by the observation that the addition of a purified p53:T antigen complex was as inhihitory as free p53 to the DNA helicase activity of free T antigen. Thus our data indicates that the targets of p53 inhibition are the functional units of T antigen, namely the hexamers.