A base-pairing interaction between U2 and U6 small nuclear RNAs occurs in > 150S complexes in HeLa cell extracts: implications for the spliceosome assembly pathway

In mammalian cells, base pairing between the U2 and U6 small nuclear RNAs is required during pre-RNA splicing. We show by psoralen crosslinking of HeLa nuclear extract that U2.U6 base pairing occurs within abundant ribonucleoprotein complexes that sediment at > 150 S in glycerol gradients. All of the spliceosomal RNAs (U1, U2, U4, U5, and U6) cosediment with these large complexes, suggesting that they may be related to small nuclear RNA-containing structures called speckles/coiled bodies or snurposomes, which have been visualized in mammalian or amphibian nuclei, respectively. In contrast to nuclear extract, S100 extract, which is splicing-defective and lacks the > 150S complexes, does not contain base-paired U2.U6. However, U2.U6 base pairs form in S100 extract that has been made splicing-competent by supplementation with Ser/Arg-rich (SR) proteins, ATP, and an adenovirus splicing substrate. During splicing in supplemented S100 extract, U2.U6 base pairing precedes the appearance of splicing intermediates and occurs initially in an approximately 60S spliceosome complex but also in progressively larger (100-300 S) complexes. Possible functional relationships between the 60S spliceosome and the > 150S complexes are discussed.     

A set of electrophoretic molecular markers for strain typing and population genetic studies of Histoplasma capsulatum

A set of eleven biallelic and three multiallelic molecular markers have been developed to analyze populations of Histoplasma capsulatum. All markers are amplified by polymerase chain reaction (PCR) and can be readily scored using minimal amounts of template DNA. The 11 biallelic loci have polymorphic restriction endonuclease sites or small insertions or deletions which may be assessed by agarose gel electrophoresis. These markers are inherited in an unambiguous manner and are ideal for assessing structure and gene flow within US populations of H. capsulatum, but are monomorphic in non-US populations. Both length and sequence variation are present in the multiallelic loci, which can be scored by direct sequencing, polyacrylamide gel electrophoresis, or single-strand conformation polymorphism (SSCP): As they are hypervariable, the multiallelic loci can be used to type isolates and to assess the level of genetic variation within populations. Preliminary results indicate that the three multiallelic markers presented are sufficient to distinguish isolates at the individual level and are polymorphic in both US and non-US populations. This collection of molecular markers will be a useful tool in population and epidemiology studies of H. capsulatum.     

Female house crickets, Acheta domesticus, prefer the chirps of large males

This study demonstrates that invertebrate acoustic signals can provide information about male phenotypic attributes, and that females can use this acoustic information in mate choice to select a phenotypically superior mate. I investigated the relationships between a male acoustic sexual signal, the phenotype of the signaller, and the female response to signal variation. I recorded and analysed the calling songs of male house crickets, Acheta domesticus. The analyses showed that chirps convey information about male size. With the exception of amplitude, the mean number of pulses per chirp was the best predictor of male size. I performed a laboratory tape-playback experiment to determine female preference during phonotaxis. Females preferred tapes playing the chirps of large males, specifically chirps with a greater number of pulses per chirp. Selection on the female preference is discussed.Copyright 1997 The Association for the Study of Animal Behaviour     

Comparing two diagnostic tests against the same "gold standard" in the same sample

Methods are proposed for comparing two diagnostic tests for the same data where a threshold for positive for each test is specified. One method contrasts the diagnostic tests' estimated risks. A second method compares the two tests' kappa coefficients. When thresholds for positive test results are specified a priori, maximum likelihood estimators and their asymptotic variances are derived and test statistics are presented for both case-control and naturalistic methods of sampling. The bootstrap is proposed as a method to assess differences in risk estimators when thresholds for positive test results are chosen by scanning the data. Examples are given to illustrate the methods.     

Outcome of patients with haemorrhagic shock: an indicator of performance in a trauma centre

The survival rate of patients admitted to the Royal Prince Alfred Hospital (RPAH) from the central Sydney area with a major injury has improved since regionalization of trauma services in early 1992. This improvement has been attributed to education, better hospital care and changing trauma epidemiology. This study was conducted to assess whether the outcome of patients admitted with haemorrhagic shock had improved. This is proposed as a more subtle indicator of hospital performance than overall survival rates. A prospective before and after study was carried out comparing outcome in the 18 months preceding 1 January 1992 with that in the subsequent 18 months. Entry criteria to the study included all primary retrievals from the central Sydney area to RPAH with injury severity scores (ISS) > 15. Outcomes were compared generally and in those who were in a state of haemorrhagic shock (systolic blood pressure < or = 90 mmHg) on arrival at the emergency department. Three hundred and eight patients were entered into the study. Stratification showed similar numbers, demographic features and mechanisms of injury in the two groups. Forty patients were in a state of haemorrhagic shock on admission. The overall mortality was reduced from 31% to 11% (P < 0.001) over the two phases of the study. The mortality from blood loss in the 40 shocked patients fell from 10/25 in the first period to 2/15 (P = 0.07) in the latter. These improved survival rates were felt to reflect the value of the educational and organizational initiatives introduced following designation of the hospital as a trauma centre.     

Automatic labeling and characterization of objects using artificial neural networks

Existing NASA supported scientific databases are usually developed and managed by a team of database administrators whose main concern is the efficiency of the databases in terms of normalization and data search constructs. The populating of the database is usually done in a manual fashion by row and column as the data become available, and the data dictionary is usually defined by the same team (at times with little input from the end science user). This process is tedious, error prone and self-limiting in terms of what can be described in a relational Data Base Management System (DBMS). The next generation Earth remote sensing platforms [i.e., Earth Observing System (EOS)] will be capable of generating data at a rate of over 300 Megabits per second from a suite of instruments designed for different applications. What is needed is an innovative approach that creates object-oriented data-bases that segment, characterize, and catalog, and are manageable in a domain-specific context, and whose contents are available interactively and in near-real-time to the user community. This paper describes work in progress that utilizes an artificial neural net approach to characterize satellite imagery of undefined objects into high-level data objects. The characterized data is then dynamically allocated to an object-oriented database where it can be reviewed and accessed by a user. The definition, development, and evolution of the overall data system model are steps in the creation of an application-driven knowledge-based scientific information system.