Messenger RNA translation in the presence of homologous and heterologous tRNA

The effect of tRNA distribution in the cell on the rate of specific protein synthesis has been investigated. A tRNA-dependent cell-free protein-synthesizing system derived from Krebs-II ascites cells has been worked out. In this system it is possible to synthesize specific proteins (egg-white proteins or globin) by the translation of oviduct or reticulocyte messenger RNA in the presence of tRNA from homologous or heterologous tissues. The rate of translation of a give messenger RNA is optimal in the presence of tRNA from the homologous tissue. The lower level of protein synthesis obtained with an excess of heterologous tRNA can be overcome by adding the homologous tRNA. Nevertheless homologous isoaccepting species partly purified by a reversed-phase chromatography or a benzoylated DEAE-cellulose column cannot fully restore the optimal synthesis, eliminating the hypothesis according to which a particular tRNA species is involved in this phenomenon. The correct distribution of tRNA is necessary for optimal translation of a messenger RNA.     

In vivo correlation between blood T2* and oxygen saturation

The in vivo relationship between blood T2* and oxygen saturation was investigated. A wide range of blood oxygen saturation levels was created in pigs by altering the ventilation rate. Blood T2* was measured in vivo in the abdominal aorta and the inferior vena cava, corresponding to each oxygen saturation level. Our results indicate that it is possible to measure blood T2* in vivo reliably with an MR technique we previously proposed. Blood T2* correlates closely with oxygen saturation levels over a wide range, and the relationship between blood T2* measured in vivo and oxygen saturation can be approximated by a linear function.     

A tRNA identity switch mediated by the binding interaction between a tRNA anticodon and the accessory domain of a class II aminoacyl-tRNA synthetase

Identity elements in tRNAs and the intracellular balance of tRNAs allow accurate selection of tRNAs by aminoacyl-tRNA synthetases. The histidyl-tRNA from Escherichia coli is distinguished by a unique G-1.C73 base pair that upon exchange with other nucleotides leads to a marked decrease in the rate of aminoacylation in vitro. G-1.C73 is also a major identity element for histidine acceptance, such that the substitution of C73 brings about mischarging by glycyl-, glutaminyl-, and leucyl-tRNA synthetases. These identity conversions mediated by the G-1.C73 base pair were exploited to isolate secondary site revertants in the histidyl-tRNA synthetase from E. coli which restore histidine identity to a histidyl-tRNA suppressor carrying U73. The revertant substitutions confer a 3-4 fold reduction in the Michaelis constant for tRNAs carrying the amber-suppressing anticodon and map to the C-terminal domain of HisRS and its interface with the catalytic core. These findings demonstrate that the histidine tRNA anticodon plays a significant role in tRNA selection in vivo and that the C-terminal domain of HisRS is in large part responsible for recognizing this trinucleotide. The kinetic parameters determined also show a small degree of anticooperativity (delta delta G = -1.24 kcal/mol) between recognition of the discriminator base and the anticodon, suggesting that the two helical domains of the tRNA are not recognized independently. We propose that these effects substantially account for the ability of small changes in tRNA binding far removed from the site of a major determinant to bring about a complete conversion of tRNA identity.     

A correlation between shoulder laxity and interfering pain in competitive swimmers

STUDY OBJECTIVE: The "impact factor" published in Science Citation Index (SCI) is widely used in the scientific community to measure the relative importance of a medical journal. In contrast to all other indicators of academic growth in emergency medicine, impact factors for emergency medicine journals have remained low and unchanged since the inception of the specialty. We wished to investigate this incongruity. METHODS: We examined the methodology used to derive the SCI's journal impact factor. RESULTS: The impact factor for journals is defined mathematically as the number of times a journal is cited over a period of time (the numerator) divided by the number of articles published by that journal during the same period (the denominator). Citation counts are derived from examination of all references contained in a subset of journals known as "source" journals. No emergency medicine journals are included in this group. The only source of citations for emergency medicine journals is from journals outside of emergency medicine. This produces small numerators with relatively constant denominators, leading to low impact factors. CONCLUSION: The apparent failure of emergency medicine journals, as measured by the SCI impact factor, to keep pace with other indicators of academic development of the field is at least in part attributable to a methodologic bias inherent in the derivation of this factor.     

Lack of correlation between EBV serology and presence of EBV in the Hodgkin and Reed-Sternberg cells of patients with Hodgkin's disease

Epstein-Barr virus (EBV) is detected in Hodgkin and Reed-Sternberg (HRS) cells in up to 50% of patients with Hodgkin's disease (HD). HD patients have been reported to express high serum titers against EBV antigens, even prior to the diagnosis of HD. Patients with high serum titers have a poorer prognosis. The aim of this study was to examine the relationship between the presence of EBV in HRS cells and the antibody titers reactive with different EBV antigens. Frozen serum and histopathological tissues were available from 107 untreated HD patients diagnosed between 1979 and 1991. The presence of EBV in the HRS cells was evaluated with immunohistochemistry directed against the LMP-1 antigen and/or with in situ hybridization of EBER-1. Analyses were performed of serum titers against early antigen (EA), diffuse (IgA and IgG) and restricted (IgG), virus-capsid antigen (VCA) (IgA and IgG), and EBV-encoded nuclear antigens (EBNA, EBNA 1, EBNA 2A, EBNA 2B, EBNA 6). EBV was detected in 27/107 (25%) tumor specimens, with a higher proportion in the MC group 8/13 (62%) (p < 0.01). IgG VCA and EBNA were detected in 99/107 (93%), evidence of a previous EBV infection. There were no significant relationships between antibody titers reactive with different EBV antigens and detectable EBV in HRS cells. Furthermore, there did not appear to be any relationship between EBV serology or the presence of EBV in HRS cells and clinical outcome. The role of EBV in the development of HD, especially its relationship to the immunological response, remains unclear.     

A correlation between membrane fluidity and the critical temperature for cell adhesion

BHK 21 cells can adhere to a protein-coated plastic dish in the presence of Ca2+ at temperatures above 12 degrees C. However, they cannot adhere below 8 degrees C. The ESR spectrum of cells spin-labeled with a stearic acid label indicated that the membrane fluidity changed characteristically at 10 degrees C, 20 degrees C, and 30 degrees C. The critical temperature for cell adhesion coincided well with one of the characteristic temperatures for the membrane fluidity change. In the case of adhesion in the presence of Mg2+, no such correlation was observed.     

A correlation between attendance and grades in a first-year psychology class.

Performed a correlational analysis of attendance records and grades in a 1st-yr psychology class. 103 undergraduates were informed that the attendance records would not affect their grades in the course. A positive correlation was found between attendance and final grades in the course. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Correlation between presence of viable bacteria and presence of endotoxin in middle-ear effusions

The presence of endotoxin (detected by the Limulus amebocyte lysate assay) was compared to the presence of viable Haemophilus influenzae and Moraxella catarrhalis (detected by PCR) in 106 middle-ear effusions from pediatric patients with chronic otitis media. Endotoxin was found in 81 of the 106 specimens. Of these 81 specimens, 66 (81.5%) also tested positive for one or both of the gram-negative bacteria H. influenzae and M. catarrhalis. The data suggest that viable gram-negative bacteria, detectable by PCR but often undetectable by culture, may be the source of endotoxin in middle-ear effusions.     

A correlation between the loss of hydrophobic core packing interactions and protein stability

The hydrophobic core packing in four-alpha-helical bundles appears to be crucial for stabilizing the protein structure. To examine the structural basis of hydrophobic stabilization, the crystal structures of the Leu-->Val (L41V) and Leu-->Ala (L41A) substitutions of the core residue Leu41 of the ROP protein have been determined. Both substitutions are destabilizing and lead to formation of cavities. The main responses to mutations are the collapse of the central part of the alpha-helix containing the site of mutation, shifts of internal water molecules, and in L41A, the trapping of a water molecule in a cavity engineered by the mutation. For both mutants, these effects limit the increase in cavity size to less than 10 A3, while an increase of 37 A3 and 100 A3 is expected for L41V and L41A, respectively, in the absence of any cavity size reducing effects. The mobility of internal side-chains is increased and in L41A, it reaches values typical for exposed residues. A parameter (Deltanh) is introduced as a measure of the number of van der Waals contacts lost. For ROP, barnase and T4 lysozyme mutants, there is a good correlation between Deltanh and the free energy of unfolding DeltaDeltaG relative to wild-type protein. The Deltanh value turns out to be more suitable for analysing structural and energetic responses to mutation than other parameter, such as cavity volumes and packing densities. Possible evolutionary implications of the DeltaDeltaG versus Deltanh relationship are discussed.     

Lack of correlation between Sendai virus P/C mRNA structure and its utilization of two AUG start sites from alternate reading frames: implications for viral bicistronic mRNAs

The polycistronic P/C mRNA of Sendai virus encodes five proteins (C', P, C, Y1, and Y2) each of which initiates from a distinct start site. Two major proteins, P and C, are expressed in approximately equimolar amounts from two consecutive AUGs in overlapping reading frames. To better understand the mechanism of expression of the C protein from a downstream AUG, site-directed mutants of the P/C mRNA were created and expressed in COS1 cells. The secondary structure of the mRNA was examined to determine whether the mRNA structure played any role in the synthesis of the C protein. Our results ruled out any significant involvement of the 5' UTR, sequence contexts, secondary structure, distance between the start sites, and sequences downstream to the C-AUG. However, they are consistent with the concept that the synthesis of the C protein is primarily dependent on the orientation of its reading frame, i.e., +1 in relation to the upstream P reading frame. The downstream reading frame was translated poorly when it occurred in +2 orientation in relation to the upstream reading frame. Interestingly, all the known functional bicistronic mRNAs with overlapping reading frames from cytoplasmic RNA viruses have their downstream reading frame in +1 orientation relative to the upstream frame. We propose that the evolutionary conservation of the downstream reading frame in +1 orientation in these bicistronic mRNAs is important for its efficient translation.     

Ventilation inhomogeneities and mixed venous blood N2 in multibreath N2 washout

OBJECTIVE: To examine the relationship between allergy-related symptoms, food intolerance and psychological distress in primary care. METHODS: Two thousand three hundred and thirty two adults in five General Practices in the South of England completed questionnaires regarding allergy-related symptoms and psychological symptoms, but no association was demonstrated between a history of diagnosed or treated asthma, eczema or hay fever and psychological morbidity. Cases of food intolerance had lower levels of psychological distress than expected compared to hospital samples. Current, but not past wheezing and eczema, was associated with an excess of life stresses in the previous six months. CONCLUSIONS: The association between psychological distress and the label of food allergy/intolerance found in specialist care does not extend to primary care.     

Clinical correlation between the premortem study and autopsy

BACKGROUND: Lately, autopsies are performed less frequently in hospitals, despite their importance as a diagnostic tool. AIM: To study the concordance between clinical diagnosis and postmortem study in patients that died in a teaching hospital. MATERIAL AND METHODS: Autopsy findings in 57 patients (aged 16 to 85 years old, 28 female) that died at a University hospital were analyzed. Clinical diagnoses were compared with those of the postmortem examination and the degree of concordance between both diagnoses was calculated. RESULTS: Seven major omissions (12.3%), whose knowledge could have changed the clinical course of patients, were detected. These omissions occurred in patients with complex diseases or due to limitations of diagnostic procedures. Also, seven omissions, found in severely ill patients, whose knowledge would not change the patient's evolution, were also detected. CONCLUSIONS: Autopsy still is a valuable tool to assess the quality of care for patients that die during their hospitalization.     

A possible correlation between vertebral artery insufficiency and degenerative changes in the cervical spine

We studied 130 patients, aged 20 to 81 years, with symptoms of tinnitus, vertigo or dizziness. Radiological examinations revealed degenerative changes in the cervical spines of all patients such as discopathy or osteophytes. Head and neck and neurological examinations ruled out other symptoms apart from vertebrobasilar artery flow insufficiency. The vertebrobasilar arteries were examined by means of a color Doppler ultrasonograph using duplex scanning. The correlation coefficient (CC) defining the relationship between the number of patients with abnormal blood flow and the total number of patients with radiologically confirmed changes in the cervical spine was 41.5%. When patients were separated by age, the value of the CC coefficient increased proportionally according to age, changing from 0 to 79.1%. Use of the Doppler ultrasonograph was found to be a safe and non-invasive diagnostic method that enabled us to assess the influence of degenerative changes in the cervical spine on hemodynamic disturbances in the inner ear and brain stem. Our findings demonstrated a pathological decrease of vertebral artery flow velocity in relationship to degenerative changes in the cervical spine.     

Chromatography and electrophoresis techniques for demonstrating the presence of cellular N6-(delta2-isopentenyl)-adenosine-3''-monophosphate

Bacteriophage T4 gene 32 encodes a DNA unwinding protein required for DNA replication, repair, and recombination. Gene 32 temperature-sensitive mutations enhance virtually all base pair substitution mutation rates.