Evidence for an RNA-based catalytic mechanism in eukaryotic nuclear ribonuclease P

Ribonuclease P is the enzyme responsible for removing the 5'-leader segment of precursor transfer RNAs in all organisms. All eukaryotic nuclear RNase Ps are ribonucleoproteins in which multiple protein components and a single RNA species are required for activity in vitro as well as in vivo. It is not known, however, which subunits participate directly in phosphodiester-bond hydrolysis. The RNA subunit of nuclear RNase P is evolutionarily related to its catalytically active bacterial counterpart, prompting speculation that in eukaryotes the RNA may be the catalytic component. In the bacterial RNase P reaction, Mg(II) is required to coordinate the nonbridging phosphodiester oxygen(s) of the scissile bond. As a consequence, bacterial RNase P cannot cleave pre-tRNA in which the pro-Rp nonbridging oxygen of the scissile bond is replaced by sulfur. In contrast, the RNase P reaction in plant chloroplasts is catalyzed by a protein enzyme whose mechanism does not involve Mg(II) coordinated by the pro-Rp oxygen. To determine whether the mechanism of nuclear RNase P resembles more closely an RNA- or a protein-catalyzed reaction, we analyzed the ability of Saccharomyces cerevisiae nuclear RNase P to cleave pre-tRNA containing a sulfur substitution of the pro-Rp oxygen at the cleavage site. Sulfur substitution at this position prohibits correct cleavage of pre-tRNA. Cleavage by eukaryotic RNase P thus depends on the presence of a thio-sensitive ligand to the pro-Rp oxygen of the scissile bond, and is consistent with a common, RNA-based mechanism for the bacterial and eukaryal enzymes.

Temporal and spatial distribution of interleukin-1 beta in balloon injured porcine coronary arteries

OBJECTIVE

Interleukin-1 beta (IL-1 beta) is a proinflammatory cytokine with a wide range of biological activities. We determined the distribution of IL-1 beta following percutaneous transluminal coronary angioplasty (PTCA) of porcine arteries, and the presence of caspase-1 (required for the activation of IL-1 beta).

METHODS

Oversized balloon angioplasty was performed in Yorkshire White pigs and the vessels excised at selected intervals (1, 6, 18 h, 3, 7, and 14 days) post-PTCA. IL-1 beta and caspase-1 were then identified using reverse transcription polymerase chain reaction (RT-PCR), in situ RT-PCR, and immunohistochemistry.

RESULTS

IL-1 beta protein was detected in the inflammatory infiltrate up to 3 days after PTCA. Luminal endothelial cells contained IL-1 beta at 1 h, with peak expression at 3-7 days. Adventitial capillaries were IL-1 beta-positive at all timepoints. IL-1 beta was detected in adventitial cells at 3 days, with reduced levels at 7 and 14 days. At 7 days, neointimal cells were also IL-1 beta positive. No IL-1 beta was detected in non-PTCA control arteries. RT-PCR demonstrated IL-1 beta mRNA expression to be induced at 1 h, and absent at 3 days. In situ RT-PCR revealed this expression to be distributed throughout the arterial layers at 6 h, but localized to the adventitia at 18 h, with a baseline expression in the adventitial layer of non-PTCA controls. Caspase-1 was detected in luminal endothelial cells from 6 h, in adventitial cells from 3 days, and in neointimal cells from 7 days post-PTCA. This expression colocalized with IL-1 beta, indicating the potential for the IL-1 beta present to become activated.

CONCLUSIONS

We conclude that IL-1 beta is synthesised, in conjunction with caspase-1, by endothelial, inflammatory, and adventitial cells early (within 3 days) after PTCA, with decreased levels at later timepoints, suggesting that it has a key role to play in the early stages of healing following PTCA.

Ultrasound enhances reporter gene expression after transfection of vascular cells in vitro

BACKGROUND

Restenosis after percutaneous coronary intervention remains a serious clinical problem. Progress in local gene therapy to prevent restenosis has been hindered by concerns over the safety and efficacy of viral vectors and the limited efficiency of nonviral techniques. This study investigates the use of adjunctive ultrasound to enhance nonviral gene delivery.

METHODS AND RESULTS

Cultured porcine vascular smooth muscle cells (VSMCs) and endothelial cells (ECs) were transfected with naked or liposome-complexed luciferase reporter plasmid for 3 hours. Ultrasound exposure (USE) for 60 seconds at 1 MHz, 0.4 W/cm2, 30 minutes into this transfection period enhanced luciferase activity 48 hours later by 7.5-fold and 2. 4-fold, respectively. Luciferase activity after lipofection of ECs was similarly enhanced 3.3-fold by adjunctive USE. USE had no effect on cell viability, although it inhibited VSMC but not EC proliferation.

CONCLUSIONS

Adjunctive USE was associated with enhanced transgene expression in VSMCs and ECs and reduced VSMC but not EC proliferation in vitro, which suggests that ultrasound-assisted local gene therapy has potential as an antirestenotic therapy.

American Association of Pharmaceutical Scientists--annual meeting and exposition: drug discovery and development. 15-19 November 1998, San Francisco, CA, USA

AAPS is the acronym for the American Association of Pharmaceutical Scientists, a relatively young organization, dedicated to the development of the pharmaceutical sciences in the widest sense, from basic research through discovery and development to regulatory affairs and marketing. The association has a membership of over 10,000 scientists, mostly in the US, but with a worldwide representation. The Annual Meeting and Exposition attract about 7000 delegates, including exhibitors. Despite its wide coverage, however, its strength lies in the development and use of technology rather than basic research. Thus in the search for lead compounds, the use of combinatorial chemistry and high-throughput screening was more evident than novel chemistry or pharmacology, and there was a preponderance of contract research organizations or service companies in the exposition. Nevertheless, the size of the meeting ensured that there was something of interest to everyone most of the time, and the areas of emphasis served as a guide to future trends in drug discovery and the direction of the industry as we approach the new millennium. Typically, at any one time, the delegate could choose amongst three round-table meetings, three symposia, three podium sessions with short papers, and numerous special interest semi-private gatherings, not to mention 2500 posters spread over six sessions during the week. This report concentrates on those aspects which contributed to novel research, or gave major pointers to future directions. Abstracts for the various papers were available to delegates as hard copy and on CD-ROM, in the form of the first supplement of an as yet unpublished all-electronic journal, to be known as PharmSci.

Apoptosis and cell proliferation after porcine coronary angioplasty

BACKGROUND

Angioplasty initiates a number of responses in the vessel wall including cellular migration, proliferation, and matrix accumulation, all of which contribute to neointima formation and restenosis. Cellular homeostasis within a tissue depends on the balance between cell proliferation and apoptosis.

METHODS AND RESULTS

Profiles of apoptosis and proliferation were therefore examined in a porcine PTCA injury model over a 28-day period. Forty-two arteries from 21 pigs, harvested at the site of maximal injury at 1, 6, and 18 hours, and 3, 7, 14, and 28 days after PTCA, were examined (n=3 animals per time point). Uninjured arteries were used as controls. Apoptosis was demonstrated by the terminal uridine nick-end labeling (TUNEL) method, transmission electron microscopy (TEM), and DNA fragmentation. Cells traversing the cell cycle were identified by immunostaining for proliferating cell nuclear antigen (PCNA). Apoptosis was not detected in control vessels at all time points nor at 28 days after PTCA. Apoptotic cells were identified at all early time points with a peak at 6 hours (5.1+/-0.26%; compared to uninjured artery, P<0.001) and confirmed by characteristic DNA ladders and TEM findings. Regional analysis showed apoptosis within the media, adventitia, and neointima peaked at 18 hours, 6 hours, and 7 days after PTCA, respectively. In comparison, PCNA staining peaked at 3 days after PTCA (7.16+/-0.29%; compared to 1.78+/-0.08% PCNA-positive cells in the uninjured artery, P<0.001). Profiles of apoptosis and cell proliferation after PTCA were discordant in all layers of the artery except the neointima. These profiles also differed between traumatized and nontraumatized regions of the arterial wall. Immunostaining with cell-type specific markers and TEM analysis revealed that apoptotic cells included vascular smooth muscle cells (VSMCs), inflammatory cells, and adventitial fibroblasts.

CONCLUSIONS

These results suggest that the profile of apoptosis and proliferation after PTCA is regional and cell specific, and attempts to modulate either of these events for therapeutic benefit requires recognition of these differences.

Do hospital palliative care teams improve symptom control? Use of a modified STAS as an evaluation tool

The support team assessment schedule (STAS) has previously been validated as an evaluation tool for community palliative care teams and inpatient units. This study reports on use of an expanded STAS (E-STAS) to determine symptom prevalence and outcome for inpatients and outpatients referred to a multiprofessional hospital palliative care team. E-STAS forms were completed on patients at referral and twice weekly thereafter. Between August 1996 and May 1997, 352 patients had one or more E-STAS forms completed; 122 of this group had three or more assessments. One-hundred-and-eighty-two patients were male and 170 were female, the median age was 68.5 years (range 26-101 years) and all but 27 (8%) had malignant disease. Of the symptoms assessed on referral, the most common were psychological distress 93%, anorexia 73%, pain 59%, mouth discomfort 59%, depression 40%, constipation 36%, breathlessness 32%, nausea 24% and vomiting 13%. In the 122 patients where three or more assessment were completed, statistically significant improvements from first to last assessment were seen in all symptoms except depression. This study suggests that E-STAS may be a useful tool to evaluate interventions by a hospital palliative care team in patients with advanced disease.

Aortoiliac aneurysm with arteriocaval fistula treated by a bifurcated endovascular stent-graft

A 71-year-old patient with high-output cardiac failure was found to have an aneurysmal distal aorta with evidence of an arteriocaval fistula on ultrasound scanning. CT demonstrated an aneurysm of the distal aorta and right common iliac artery and an intraarterial digital subtraction angiogram confirmed an arteriocaval fistula. In view of the patient's cardiac failure and general condition an endovascular stent was considered. The right internal iliac artery was occluded with Tungsten coils prior to the insertion of a bifurcated stent-graft. This resulted in total occlusion of the aneurysm and obliteration of the arteriocaval fistula. To our knowledge such a case has not been previously reported.

A randomized controlled trial of double-versus single-gloving in vascular surgery

With the increasing incidence of hepatitis B and HIV, and the increasing awareness of the risk and prevalence of hepatitis C, it is becoming even more necessary to adopt stricter policies to safeguard personnel and to reduce the risk of transmission. Previous studies have shown a need for eye protection, protective clothing and the use of double-gloving during operative or interventional procedures. The risk of infection is much less with unbroken skin and conversely more likely when hollow needles are used. Arguments against the routine use of double-gloving include the loss of dexterity and the discomfort incurred, and the potential loss of dexterity that might theoretically result in more rather than fewer needle-stick injuries.

Transplantation of myoblasts from a transgenic mouse overexpressing dystrophin prduced only a relatively small increase of dystrophin-positive membrane

Myoblast cultures from normal and Tg-MDA (transgenic mouse overexpressing dystrophin 50-fold) mice were transplanted into dystrophin-deficient mdx mouse muscles. Four weeks after transplantation, dystrophin-positive fibers were observed four times more frequently in cross sections of muscles injected with Tg-MDA. Myoblasts from Tg-MDA mice also expressing the beta-gal transgene (Tg-MDA/beta-gal) and myoblasts from beta-gal transgenic mice containing one normal dystrophin gene (normal/beta-gal) were also transplanted into mdx mouse muscles. Four weeks after transplantation, the fiber length positive for dystrophin (nuclear domain) was shorter (439 +/- 326 microm) than the beta-gal nuclear domain (1466 +/- 713 microm) of the same fiber when normal/beta-gal myoblasts were transplanted, but increased (1302 +/- 487 microm) when Tg-MDA/beta-gal myoblasts were used. These experiments show that despite the presence in Tg-MDA myoblasts of constructions which lead in vivo in transgenic mice to an overexpression of dystrophin 50-fold, the membrane area over which dystrophin was expressed was increased only threefold. This observation is also expected for vector-mediated gene therapy.

Isozyme variation in Calliandra calothyrsus (Leguminosae): its implications for species delimitation and conservation

Patterns of genetic diversity within and among populations of Calliandra calothyrsus, an important multipurpose tree species, were examined using isozyme analysis. C. calothyrsus is a widespread species distributed throughout Central America and southern Mexico, across a variety of environments. Morphologically and ecologically distinct populations can be identified within this range, but they are currently considered to represent a single species. C. calothyrsus has been introduced to many parts of the tropics, where it is cultivated as a source of fuelwood, animal fodder, green manure, and shade by rural communities. Some of these introductions are known to have originated from Guatemala, but very little is known about the genetic diversity of either the native or naturalized populations. Isozyme electrophoresis of 23 loci across 17 populations of C. calothyrsus indicated that the majority of genetic diversity was partitioned between populations (FST = 0.802) and that within-population heterozygosity was low (mean Ho = 0.057). Naturalized populations had lower than expected heterozygosities and were most similar to material from Santa Maria de Jesus, a natural population in southern Guatemala. Four distinct groups of populations were identified on the basis of Nei's genetic distances and Population Aggregation Analysis (PAA), and correlate with the morphological and ecological differences that can be observed within the species. The results are discussed in relation to species delimitation and conservation.

Experimental autoimmune uveitis in HLA-B27 transgenic mice

The major histocompatibility complex (MHC) gene, HLA-B27 is strongly associated with auto-immune uveitis and spondyloarthropathies in humans. Experimental mouse models of autoimmune uveitis involve systemic immunization with the retinal autoantigen interphotoreceptor retinoid binding protein (IRBP). To assess possible roles of HLA-B27 in autoimmune uveitis, as well as to investigate a possible new animal model of human uveitis, inbred strains of C57BL/6 and C57BL/6 possessing the human HLA-B27 or HLA-A2 transgene were immunized with IRBP emulsified in complete Freund's adjuvant (CFA). Dilated eye examinations were performed to assess the timing and clinical course of any ensuing uveitis. Mice were sacrificed 3 to 4 weeks postinjection and the eyes submitted for histopathologic analysis. CFA alone did not produce any clinical uveitis. Fifty percent of eyes from the background C57BL/6 strain developed uveitis as early as 10 days postinjection. Of the eyes demonstrating uveitis, an average clinical score of 2.5 was present. Pathologically, a moderate scleritis and anterior uveitis was present. Fifty percent of A2 transgenic eyes developed uveitis as early as 14 days postinjection with an average clinical score of 2.0. Pathologically, a mild vitritis was present. Uveitis developed in only 20% of B27 transgenic mice and reached a peak on day 28. The average EAU score in diseased animals was 4.5. A dense retinitis and panuveitis was associated with severe vitritis. We conclude that the presence of the B27 gene is associated with a decreased incidence and slower rate of onset of EAU following immunization with IRBP; however, EAU may be more severe in the HLA-B27 expressing animals who do develop disease.

Nuclear pre-tRNA terminal structure and RNase P recognition

Nuclear pre-tRNA transcripts often contain an extension of the aminoacyl stem formed by base pairing between the 5'-leader and 3'-trailing sequences, but the -1 position preceding the mature 5' end is usually left unpaired. Considering recently proposed tertiary structural models for RNase P RNAs, we hypothesize that the -1 mismatch prevents a strong, coaxially extended aminoacyl stem, which might otherwise sterically interfere with substrate positioning in the RNase P active site. This hypothesis is tested by creating uninterrupted aminoacyl stem extensions in four nuclear tRNA precursors that normally have a mismatched nucleotide at position -1, and comparing their cleavage rates with those of the normal precursors. Determinations of Km and kcat values for a normal and an altered pre-tRNA(SUP53), which exhibits the most subtle structural alteration immediately upstream of the cleavage site, indicate that the mismatch at position -1 is an important structural requirement for both substrate affinity and efficient catalysis (and/or product release) by nuclear RNase P. This conclusion is further supported in vivo, where the pre-tRNA(SUP53) mutant precursor lacking the -1 mismatch is shown to accumulate.

A randomized controlled trial of the cost-effectiveness of a district co-ordinating service for terminally ill cancer patients

The objective of this paper is to compare the cost effectiveness of a co-ordination service with standard services for terminally ill cancer patients with a prognosis of less than one year. We designed a randomized controlled trial, with patients randomized by the general practice with which they were registered. Co-ordination group patients received the assistance of two nurse coordinators whose role was to ensure that patients had access to appropriate services. The setting was in a South London health authority. Complete service use and outcome data were collected on 167 patients, 86 in the co-ordination group, and 81 in the control group. Our results, as previously reported, show that no differences in outcomes were detected between the co-ordination and control groups; the mean total costs incurred by the co-ordination group were significantly less than those of the control group. The co-ordinated group used significantly fewer inpatient days (mean 24 versus 40 inpatient days; t = 2.4, p = 0.002) and nurse home visits (mean 14.5 versus 37.5 visits; t = 0.3, p = 0.01). Mean cost per co-ordinated patient was almost half that of the control group patients 4774 pounds versus 8034 pounds, t = 2.8, p = 0.006). Although the unit cost data were relatively crude, these cost reductions were insensitive to a wide range of unit costs. These differences persisted when, in order to control for any putative differences in severity between the two groups, the analysis was restricted to patients who had died by the end of the study. The ratio of potential cost savings to the cost of co-ordination service was between 4:1 and 8:1. In conclusion, the co-ordination service for cancer patients who were terminally ill with a prognosis of less than one year was more cost effective than standard services, due to achieving the same outcomes at lower service use, particularly inpatient days in acute hospital. Assuming that the observed effects are real, improved co-ordination of palliative care offers the potential for considerable savings. Further research is needed to explore this issue.