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Biomedical subjects

L Simpson

Publications and source records attributed to L Simpson.

At least 91 records · Page 5Linked to original sources
PubMed1995

RNA-protein interactions in the ribonucleoprotein T-complexes in a mitochondrial extract from Leishmania tarentolae.

We have investigated protein-RNA interactions and the incorporation of [alpha-32P]UTP into the guide RNA and mRNA components of the 'T-complexes' in a mitochondrial extract from Leishmania tarentolae. The terminal uridylyl transferase-containing complex T-IV is probably involved in the maturation of the 3'-oligo(U) tail of the gRNAs, but the biological function and biochemical nature of the remaining T-complexes is not known. We have found that the relative extent of labeling of the RNA components is dependent on the UTP concentration: at low levels, the main endogenous RNA components labeled are the gRNAs in T-IV; at higher levels, the mRNAs in all of the T-complexes are preferentially labeled. We also show a tentative correlation in the migration pattern of UTP-labeled T-complexes and complexes which bind exogenous labeled RNA. The relative extent of binding to specific complexes is dependent upon the type of RNA. Most of the interactions between the labeled RNAs and proteins can be disrupted by heparin or a large excess of rRNA, but two labeled complexes were resistant to competition. Most of the binding of labeled exogenous gRNA is disrupted by competition with a large excess of rRNA, but predigestion of the extract with micrococcal nuclease and saturation with rRNA uncovered a high affinity complex, which involves at least two proteins interacting with the bound gRNAs. A knowledge of the RNA and protein components may aid in understanding the biological roles of these RNP complexes.

Animals↗
PubMed1995

Caffeine enhances doxorubicin cardiac toxicity in an animal model.

Based on in vitro data suggesting an interaction between methylxanthines and doxorubicin in regulating Ca2+ across muscle sarcoplasmic reticulum, this study was designed to test the hypothesis that a commonly used methylxanthine, caffeine, might influence the cardiac toxicity of doxorubicin. Three days following doxorubicin treatment, in vivo intracardiac pressures, cardiac outputs, in vitro cardiac weights, and cardiac electron microscopy were performed. Guinea pigs were treated with doxorubicin alone, doxorubicin plus caffeine, caffeine alone, and sterile saline as a control measure. Animals treated with doxorubicin had no significant differences in in vivo hemodynamics compared to the control animals. The average histology score was slightly but not statistically greater than the control animals, score (1.19 +/- 0.36 vs 1.60 +/- 0.34, respectively, P = NS). Animals receiving both doxorubicin and caffeine compared to the control animals had important differences in left ventricular systolic pressure (67 +/- 10 vs 92 +/- 7 mmHg; P = .003), cardiac output (154 +/- 35 vs 217 +/- 41 mL/min; P = .0174), stroke volume (.59 +/- 12 vs .79 +/- .07 mL; P = .0045), and histology score (2.36 +/- 0.21 vs 1.19 +/- 0.36; P = .028). There were no differences in left or right heart filling pressures between treatment groups. As an independent confirmation, there was a weak but statistically significant negative correlation between the biopsy score and cardiac output or stroke volume for all four groups of animals (r = .44, P = .031 and r = -.42, P = .040, respectively). These data are consistent with caffeine and doxorubicin having additive or potentiating effects on cardiac toxicity in this animal model.

Animals↗
PubMed1995

Minicircle-encoded guide RNAs from Crithidia fasciculata.

Although the mitochondrial uridine insertion/deletion, guide RNA (gRNA)-mediated type of RNA editing has been described in Crithidia fasciculata, no evidence for the encoding of gRNAs in the kinetoplast minicircle DNA has been presented. There has also been a question as to the capacity of the minicircle DNA in this species to encode the required variety of gRNAs, because the kinetoplast DNA from the C1 strain has been reported as essentially containing a single minicircle sequence class. To address this problem, the genomic and mature edited sequences of the MURF4 and RPS12 cryptogenes were determined and a gRNA library was constructed from mitochondrial RNA. Five specific gRNAs were identified, two of which edit blocks within the MURF4 mRNA, and three of which edit blocks within the RPS12 mRNA. The genes for these gRNAs are all localized with identical polarity within one of the two variable regions of specific minicircle molecules, approximately 60 bp from the "bend" region. These minicircles were found to represent minor sequence classes representing approximately 2% of the minicircle DNA population in the network. The major minicircle sequence class also encodes a gRNA at the same relative genomic location, but the editing role of this gRNA was not determined. These results confirm that kinetoplast minicircle DNA molecules in this species encode gRNAs, as is the case in other trypanosomatids, and suggest that the copy number of specific minicircle sequence classes can vary dramatically without an overall effect on the RNA editing system.

Amino Acid Sequence↗
PubMed1995

The role of social change in preventing low birth weight.

The authors of this article examine the relationship between social factors and low birth weight and the ways in which disparities in socioeconomic status have been addressed over time. The evidence regarding the effectiveness of various efforts to influence birth weight by mitigating the consequences of disadvantage are also assessed. Low socioeconomic status has been shown to influence low birth weight through its various correlates. Historically and today, most programs and policies directed at low birth weight prevention attempt to address the individual health consequences of economic and social disadvantage. By and large, these efforts have produced mixed results. Efforts to affect low birth weight by addressing the underlying causes of social and economic disadvantage have been similarly inconclusive, reflecting the paucity of research on the subject, as well as the historical and ongoing failure to make the research link between health and social policy. The authors argue that reducing persistent disparities in low birth weight requires several steps, including embracing a broader definition of health which incorporates social dimensions, recasting the focus of research and interventions from pregnancy outcomes and infant health exclusively to include the notion of women's health more globally, expanding the research agenda to unravel the paradox of socioeconomic factors and health, and pursuing a dedicated, national commitment to assuring adequate support to individuals and families, including both adequate income and health care.

Female↗
PubMed1995

Organization and complexity of minicircle-encoded guide RNAs in Trypanosoma cruzi.

The previously observed extensive sequence heterogeneity of the kinetoplast minicircle DNA in Trypanosoma cruzi, both intra- and interstrain, has raised the question as to how the minicircle DNA in this species can have any guide RNA (gRNA)-coding capacity at all, because there do not appear to be any variable-region sequences conserved between different strains. To address this question, we obtained the complete edited sequence of maxicircle unidentified reading frame 4 mRNA and identified 25 cognate gRNAs from gRNA libraries constructed from two clonal strains of T. cruzi--Sylvio X10/CL1 and CAN III/CL1. Libraries of PCR-amplified minicircle-variable regions were also constructed for both strains. A single gene for each gRNA was identified in the same polarity within specific minicircle-variable regions from both strains, 60-100 nt downstream from the conserved 12mer sequence. GTP-capped total gRNA from one strain failed to cross-hybridize with minicircle DNA from the other strain. The explanation for this proved to be the number of polymorphisms, mainly transitions, within the homologous gRNAs in the two strains. In most cases, these transitions did not destroy the edited mRNA/gRNA base pairing, as a result of the allowed G-U wobble base pairing. The sequences of the variable regions containing homologous gRNAs in the two strains probably derived from an ancestral sequence, and each has accumulated sufficient polymorphisms so as not to allow hybridization. Within a strain, multiple redundant gRNAs were identified that encode identical editing information but have different sequences.

Amino Acid Sequence↗
PubMed1995

Kidney Stone Center of the Pacific. Summary of operations 1986 to 1993.

The history and operational results in the six years since the Kidney Stone Center of the Pacific opened in 1986 are summarized and compared to the published literature, with particular attention to Hawaii's unique racial composition. We hope that the results will enable us to improve our management of stones in the future.

Adolescent↗
PubMed1994

Disruption of RNA editing in Leishmania tarentolae by the loss of minicircle-encoded guide RNA genes.

RNA editing in kinetoplastids appears to be a labile genetic trait that is affected by prolonged cell culture. The transcripts of the G1-G5 cryptogenes are pan-edited in the recently isolated LEM125 strain of Leishmania tarentolae, but not in the UC strain which has been in culture for 55 years. At least 32 minicircle-encoded guide RNAs (gRNAs) for the editing of G1-G5 transcripts are present in LEM125 and absent in UC. We hypothesize that specific minicircle sequence classes encoding gRNAs for the editing of these transcripts were lost during the long culture history of the UC strain. The protein products, which include components of complex I of the respiratory chain, are probably not required during the culture stage of the Leishmania life cycle.

Amino Acid Sequence↗
PubMed1994

Characterization of two classes of ribonucleoprotein complexes possibly involved in RNA editing from Leishmania tarentolae mitochondria.

The molecular mechanism of RNA editing in trypanosomatid mitochondria is an unsolved problem. We show that two classes of ribonucleoprotein complexes exist in a mitochondrial extract from Leishmania tarentolae and appear to be involved in RNA editing. The 'G' class of RNP complexes consists of 170-300 A particles which contain guide RNAs and proteins, show little terminal uridylyl transferase (TUTase) activity and exhibit an in vitro RNA editing-like activity. The 'T' class consists of approximately six RNP complexes, the endogenous RNA of which can be self-labeled with [alpha-32P]UTP. The most abundant T complex, T-IV, is visualized by electron microscopy as 80-140 A particles. This complex exhibits TUTase activity in the native gel and contains guide RNAs. Both G and T complexes are possibly involved with RNA editing in vivo. These results are a starting point for the analysis of the biochemistry of RNA editing.

Animals↗
PubMed1994

Evolution of RNA editing in kinetoplastid protozoa.

The editing of RNA in trypanosomatid mitochondria involves the insertion and occasional deletion of uridine residues within coding regions of maxicircle messenger RNA transcripts. The extent to which the transcripts of homologous genes undergo editing differs in different species. In some, entire genes are edited (pan-editing), whereas in others, editing is limited to the 5' termini of editing domains (5' editing). Here we investigate which type of editing is ancestral and which is derived, by analysing RNA editing in the different lineages, using a kinetoplastid phylogeny reconstructed from nuclear small subunit ribosomal RNA sequences. We conclude that the ancestral cryptogenes were pan-edited, and we hypothesize that the 5'-edited homologues were generated by several independent events from partially edited RNAs, in which case editing may be a more primitive mechanism than previously thought.

Adenosine Triphosphatases↗
PubMed1994

Ancient origin of RNA editing in kinetoplastid protozoa.

A rooted phylogenetic tree of the kinetoplastid protozoa has been constructed that, together with a comparative analysis of editing of several genes, leads to the surprising conclusion that extensive or pan-editing with multiple overlapping guide RNAs is more ancient than 5'-editing. The mechanism of editing is still uncertain, but multiple ribonucleoprotein complexes have been identified that contain components of the enzymatic machinery.

Animals↗
PubMed1994

RNA editing and mitochondrial genomic organization in the cryptobiid kinetoplastid protozoan Trypanoplasma borreli.

The bodonids and cryptobiids represent an early diverged sister group to the trypanosomatids among the kinetoplastid protozoa. The trypanosome type of uridine insertion-deletion RNA editing was found to occur in the cryptobiid fish parasite Trypanoplasma borreli. A pan-edited ribosomal protein, S12, and a novel 3'- and 5'-edited cytochrome b, in addition to an unedited cytochrome oxidase III gene and an apparently unedited 12S rRNA gene, were found in a 6-kb fragment of the 80- to 90-kb mitochondrial genome. The gene order differs from that in trypanosomatids, as does the organization of putative guide RNA genes; guide RNA-like molecules are transcribed from tandemly repeated 1-kb sequences organized in 200- and 170-kb molecules instead of minicircles. The presence of pan-editing in this lineage is consistent with an ancient evolutionary origin of this process.

Animals↗
PubMed1993

Ozone inhalation stimulates expression of a neutrophil chemotactic protein, macrophage inflammatory protein 2.

Short-term exposure of humans and animals to ozone results in increased lung neutrophils; however, the mechanisms underlying this response are not completely understood. We examined the potential involvement of the neutrophil chemotactic factor, macrophage inflammatory protein 2 (MIP-2), in ozone-induced inflammation. Exposure-response relationships for ozone and MIP-2 expression were characterized by exposing C57B1/6 mice to 0.1-2 ppm ozone for 3 hr and determining lung levels of MIP-2 mRNA 6 hr after exposure. Temporal relationships between ozone and MIP-2 were determined by exposing mice (2 ppm ozone x 3 hr) and characterizing MIP-2 mRNA expression 0, 2, 6, and 24 hr after exposure. Neutrophils in lung lavage fluid were determined in both exposure-response and time course studies. Ozone concentrations > or = 1.0 ppm increased MIP-2 mRNA and this increase corresponded with recruitment of neutrophils. MIP-2 mRNA was increased immediately after ozone exposure and decreased to control levels by 24 hr. To examine the role of direct oxidant effects in ozone-induced MIP-2 expression, alveolar macrophages were exposed in vitro for 4 hr to 10(-10)-10(-5) M hydrogen peroxide and MIP-2 expression was characterized. MIP-2 mRNA levels in lung macrophages were increased by > or = 10(-9) M hydrogen peroxide. In summary, our findings suggest the chemotactic protein MIP-2 may be responsible, at least in part, for ozone-induced increases in lung neutrophils and indicate that direct exposure of alveolar macrophages to an oxidant is sufficient to induce MIP-2 expression.

Administration, Inhalation↗