Creating a framework for the prioritization of biosecurity risks to the New Zealand dairy industry.

The New Zealand dairy sector relies on robust biosecurity measures to control and mitigate a wide range of threats to the industry. To optimize the prioritization of organisms and manage the risk they pose to the sector in a transparent and credible way, the Dairy Biosecurity Risk Evaluation Framework (D-BRiEF) was developed. This comprehensive framework was specifically designed for decision support, using a standardized approach to address the full spectrum of biosecurity threats to the sector, including exotic and endemic animal disease organisms, pest plants and insects. D-BRiEF is underpinned by three main processes, namely (i) hazard identification; (ii) multicriteria risk assessment; and (iii) communication for risk management. Expert knowledge and empirical data, including associated uncertainty, are harnessed in a standardized format. Results feed into a probability-impact model that was developed in close collaboration with dairy sector economists to provide overall comparative 10-year quantitative economic impact estimates for each assessed risk organism. A description of the overarching framework, which applies to diverse organism groups, is presented with detailed methodology on both endemic and exotic animal disease risk organisms. Examples of visual outputs are included, although actual ranking results are not reported due to industry confidentiality. D-BRiEF can provide a decision advantage to DairyNZ biosecurity risk managers and sector stakeholders by creating a transparent process that can be interrogated and updated at multiple levels to fully understand the layers of risk posed by different organisms.

An array of virtual Frisch-grid CdZnTe detectors and a front-end application-specific integrated circuit for large-area position-sensitive gamma-ray cameras.

We developed a robust and low-cost array of virtual Frisch-grid CdZnTe detectors coupled to a front-end readout application-specific integrated circuit (ASIC) for spectroscopy and imaging of gamma rays. The array operates as a self-reliant detector module. It is comprised of 36 close-packed 6 × 6 × 15 mm(3) detectors grouped into 3 × 3 sub-arrays of 2 × 2 detectors with the common cathodes. The front-end analog ASIC accommodates up to 36 anode and 9 cathode inputs. Several detector modules can be integrated into a single- or multi-layer unit operating as a Compton or a coded-aperture camera. We present the results from testing two fully assembled modules and readout electronics. The further enhancement of the arrays' performance and reduction of their cost are possible by using position-sensitive virtual Frisch-grid detectors, which allow for accurate corrections of the response of material non-uniformities caused by crystal defects.

Network science and the effects of music preference on functional brain connectivity: from Beethoven to Eminem.

Most people choose to listen to music that they prefer or 'like' such as classical, country or rock. Previous research has focused on how different characteristics of music (i.e., classical versus country) affect the brain. Yet, when listening to preferred music--regardless of the type--people report they often experience personal thoughts and memories. To date, understanding how this occurs in the brain has remained elusive. Using network science methods, we evaluated differences in functional brain connectivity when individuals listened to complete songs. We show that a circuit important for internally-focused thoughts, known as the default mode network, was most connected when listening to preferred music. We also show that listening to a favorite song alters the connectivity between auditory brain areas and the hippocampus, a region responsible for memory and social emotion consolidation. Given that musical preferences are uniquely individualized phenomena and that music can vary in acoustic complexity and the presence or absence of lyrics, the consistency of our results was unexpected. These findings may explain why comparable emotional and mental states can be experienced by people listening to music that differs as widely as Beethoven and Eminem. The neurobiological and neurorehabilitation implications of these results are discussed.

Summer (subarctic) versus winter (subtropic) production affects spinach (Spinacia oleracea L.) leaf bionutrients: vitamins (C, E, Folate, K1, provitamin A), lutein, phenolics, and antioxidants.

Comparison of spinach (Spinacia oleracea L.) cultivars Lazio and Samish grown during the summer solstice in the subarctic versus the winter solstice in the subtropics provided insight into interactions between production environment (light intensity), cultivar, and leaf age/maturity/position affecting bionutrient concentrations of vitamins (C, E, folate, K1, provitamin A), lutein, phenolics, and antioxidants. Growing spinach during the winter solstice in the subtropics resulted in increased leaf dry matter %, oxidized (dehydro) ascorbic acid (AsA), α- and γ-tocopherol, and total phenols but lower reduced (free) AsA, α-carotene, folate, and antioxidant capacity compared to summer solstice-grown spinach in the subarctic. Both cultivars had similar bionutrients, except for higher dehydroAsA, and lower α- and γ-tocopherol in 'Samish' compared to 'Lazio'. For most bionutrients measured, there was a linear, and sometimes quadratic, increase in concentrations from bottom to top canopy leaves. However, total phenolics and antioxidant capacity increased basipetally. The current study has thus demonstrated that dehydroAsA, α-tocopherol, and γ-tocopherol were substantially lower in subarctic compared to subtropical-grown spinach, whereas the opposite relationship was found for antioxidant capacity, α-carotene, and folates (vitamin B9). The observations are consistent with previously reported isolated effects of growth environment on bionutrient status of crops. The current results clearly highlight the effect of production environment (predominantly radiation capture), interacting with genetics and plant phenology to alter the bionutrient status of crops. While reflecting the effects of changing growing conditions, these results also indicate potential alterations in the nutritive value of foods with anticipated shifts in global climatic conditions.

Relationship between fresh-packaged spinach leaves exposed to continuous light or dark and bioactive contents: effects of cultivar, leaf size, and storage duration.

Current retail marketing conditions allow produce to receive artificial light 24 h per day during its displayed shelf life. Essential human-health vitamins [ascorbic acid (vit C), folate (vit B(9)), phylloquinone (vit K(1)), alpha-tocopherol (vit E), and the carotenoids lutein, violaxanthin, zeaxanthin, and beta-carotene (provit A)] also are essential for photosynthesis and are biosynthesized in plants by light conditions even under chilling temperatures. Spinach leaves, notably abundant in the aforementioned human-health compounds, were harvested from flat-leaf 'Lazio' and crinkle-leafed 'Samish' cultivars at peak whole-plant maturity as baby (top- and midcanopy) and larger (lower-canopy) leaves. Leaves were placed as a single layer in commercial, clear-polymer retail boxes and stored at 4 degrees C for up to 9 days under continuous light (26.9 micromol.m(2 ).s) or dark. Top-canopy, baby-leaf spinach generally had higher concentrations of all bioactive compounds, on a dry weight basis, with the exception of carotenoids, than bottom-canopy leaves. All leaves stored under continuous light generally had higher levels of all bioactive compounds, except beta-carotene and violaxanthin, and were more prone to wilting, especially the flat-leafed cultivar. All leaves stored under continuous darkness had declining or unchanged levels of the aforementioned bioactive compounds. Findings from this study revealed that spinach leaves exposed to simulated retail continuous light at 4 degrees C, in clear plastic containers, were overall more nutritionally dense (enriched) than leaves exposed to continuous darkness.

Lipophilic components of the brown seaweed, Ascophyllum nodosum, enhance freezing tolerance in Arabidopsis thaliana.

Extracts of the brown seaweed Ascophyllum nodosum enhance plant tolerance against environmental stresses such as drought, salinity, and frost. However, the molecular mechanisms underlying this improved stress tolerance and the nature of the bioactive compounds present in the seaweed extracts that elicits stress tolerance remain largely unknown. We investigated the effect of A. nodosum extracts and its organic sub-fractions on freezing tolerance of Arabidopsis thaliana. Ascophyllum nodosum extracts and its lipophilic fraction significantly increased tolerance to freezing temperatures in in vitro and in vivo assays. Untreated plants exhibited severe chlorosis, tissue damage, and failed to recover from freezing treatments while the extract-treated plants recovered from freezing temperature of -7.5 degrees C in in vitro and -5.5 degrees C in in vivo assays. Electrolyte leakage measurements revealed that the LT(50) value was lowered by 3 degrees C while cell viability staining demonstrated a 30-40% reduction in area of damaged tissue in extract treated plants as compared to water controls. Moreover, histological observations of leaf sections revealed that extracts have a significant effect on maintaining membrane integrity during freezing stress. Treated plants exhibited 70% less chlorophyll damage during freezing recovery as compared to the controls, and this correlated with reduced expression of the chlorphyllase genes AtCHL1 and AtCHL2. Further, the A. nodosum extract treatment modulated the expression of the cold response genes, COR15A, RD29A, and CBF3, resulting in enhanced tolerance to freezing temperatures. More than 2.6-fold increase in expression of RD29A, 1.8-fold increase of CBF3 and two-fold increase in the transcript level of COR15A was observed in plants treated with lipophilic fraction of A. nodosum at -2 degrees C. Taken together, the results suggest that chemical components in A. nodosum extracts protect membrane integrity and affect the expression of stress response genes leading to freezing stress tolerance in A. thaliana.

Pre-extraction preparation (fresh, frozen, freeze-dried, or acetone powdered) and long-term storage of fruit and vegetable tissues: effects on antioxidant enzyme activity.

Activities of the antioxidant enzymes ascorbate peroxidase, catalase, dehydroascorbate reductase, glutathione reductase, guaiacol peroxidase, monodehydroascorbate reductase, and superoxide dismutase were assayed in honeydew (Cucumis melo L.) fruit and spinach (Spinacia oleracea L.) leaves either as fresh, frozen to -80 degrees C, frozen in liquid nitrogen, freeze-dried, or acetone powder, representing the various ways tissues are treated prior to enzyme extraction. Treated tissues were analyzed following treatment or stored for up to 8 weeks at -80 degrees C. Enzyme activities in fruit frozen with or without liquid nitrogen and leaves frozen with or without liquid nitrogen or freeze-dried were equal to those of fresh tissue. Enzyme activities in freeze-dried or acetone-powdered fruit and leaves and in acetone-powdered tissues were significantly higher or lower than those in fresh tissue. Enzyme activities in both tissues frozen with or without liquid nitrogen and stored for 8 weeks at -80 degrees C changed little; those in freeze-dried and acetone-powdered tissues, however, significantly increased/decreased over the same period. Fresh tissue should be used in antioxidant enzyme assays, but if storage is necessary, tissues should be placed directly into a -80 degrees C freezer.

Assessment of ileoanal pouch inflammation by interleukin 1beta and interleukin 8 concentrations in the gut lumen.

PURPOSE: The cytokines interleukin 1beta and interleukin 8 have previously been shown to be present in mucosal biopsy specimens from inflamed ileoanal pouches. Our aim was to use the method of whole gut lavage fluid to measure cytokine concentrations and relate these to disease activity. METHODS: Forty-two patients with ulcerative colitis were recruited (23 males). Their ages ranged from 20 to 73 years (median 39). A questionnaire was completed and whole gut lavage, pouchoscopy, and biopsy were performed. RESULTS: Both interleukin 1beta and interleukin 8 were present in the whole gut lavage fluid of ileoanal pouches, with concentrations ranging from 4 to 143 pg/ml (median 6.3 pg/ml) for whole gut lavage fluid interleukin 1beta and from 18 to 1000 pg/ml (median 53.7 pg/ml) for whole gut lavage fluid interleukin 8. Whole gut lavage fluid interleukin 1beta and interleukin 8 were simultaneously detectable in 24 patients. These included the five patients with pouchitis, who had higher levels of interleukin 1beta (75 pg/ml vs. 8 pg/ml, P < 0.005) and interleukin 8 (668 pg/ml vs. 106 pg/ml, P < 0.005) compared with the rest of the patients with detectable cytokines (n = 19). The sensitivity of whole gut lavage fluid interleukin 8 (>200 pg/ml) in the diagnosis of pouchitis was 1, and the specificity was 0.86. There was a significant positive correlation of both whole gut lavage fluid interleukin 1beta and interleukin 8 with all the gut protein loss markers (immunoglobulin G, albumin, alpha1-antitrypsin). CONCLUSION: Cytokine interleukin 1beta and interleukin 8 concentrations, along with other parameters of inflammation, are raised in pouchitis in the whole gut lavage. The results also suggest a spectrum of severity of "pouchitis," with clinical pouchitis fulfilling Moskowitz criteria at the severe end of the spectrum.

Using a modified ferrous oxidation-xylenol orange (FOX) assay for detection of lipid hydroperoxides in plant tissue.

The ferrous oxidation-xylenol orange (FOX) assay was adapted for quantifying lipid hydroperoxides (LOOHs) in plant extracts. Excised pieces of several fruit and vegetable species were exposed to 83 kJ m(-2) day(-1) of biologically effective ultraviolet B irradiance (UV-B(BE)) for 10-12 days to induce cellular oxidation. The LOOH and thiobarbituric acid reactive substance (TBARS) concentrations of these plant tissues were assessed with the FOX and iodometric assays for the former and a modified TBARS assay for the latter. There was generally good agreement between the FOX and iodometric methods both prior to and following the UV exposure. However, the iodometric assay appeared to have some difficulty in consistently quantifying lower LOOH levels (<11 microM), whereas the FOX assay measured LOOH concentrations as low as 5 microM. All tissues exhibited UV-induced increases in TBARS, indicating a marked degree of cellular oxidation in the exposed tissue segments. Compared with the iodometric assay, the FOX method consistently generated less variable LOOH values. The presence of authentic linoleic acid-OOHs in spiked avocado and spinach samples (11 microM) was identified with liquid chromatography-mass spectrometry techniques, which validated corresponding FOX assay results. The FOX method is inexpensive, is not sensitive to ambient O2 or light levels, and can rapidly generate LOOH measurements. The physiological value of the FOX assay resides in its ability to measure initial rather than more advanced fatty acid oxidation; hence, early membrane-associated stress events in plant tissue can be detected.

Surgical adhesives for laser-assisted wound closure.

Solid protein solder-doped polymer membranes were developed for laser-assisted tissue repair. Biodegradable polymer membranes of controlled porosity were fabricated with poly(L-lactic-co-glycolic acid) (PLGA), poly(ethylene glycol) (PEG), and salt particles, using a solvent-casting and particulate-leaching technique. The membranes provided a porous scaffold that readily absorbed the traditional protein solder composed of serum albumin, indocyanine green dye, and de-ionized water. In vitro investigations were conducted to assess the influence of various processing parameters on the strength of tissue repairs formed using the new membranes. These parameters included PLGA copolymer and PLGA/PEG blend ratios, membrane pore size, initial albumin weight fraction, and laser irradiance used to denature the solder. Altering the PLGA copolymer ratio had little effect on repair strength, however such variations are known to influence the degradation rate of the membranes. The repair strength increased with increased membrane pore size and bovine serum albumin concentration. The addition of PEG during the membrane casting stage increased the flexibility of the membranes but not necessarily the repair strength. Typically, the repair strength increased with increasing irradiance from 12 to 18 W/cm(2). The new solder-doped polymer membranes provided all of the benefits associated with solid protein solders including high repair strength and improved edge coaptation. In addition, the flexible, moldable nature of the new membranes offers the capability of tailoring the membranes to a wide range of clinically relevant geometries.

Magnetic resonance imaging study of the congenital clubfoot treated with the Ponseti method.

Little information exists about the degree of efficacy of the several nonoperative treatments, such as manipulation and casting, used in correcting the pathology of the virgin clubfoot deformity. The steps in the correction of the displacements and anomalies of the skeletal components have never been visualized. The method reported to have the best long-term results is that of Ponseti. A magnetic resonance imaging protocol was devised to image the described chondroosseous abnormalities of the virgin clubfoot deformity and to illustrate the changes that occur with the Ponseti method of treatment. Scans were performed at the beginning of, in the middle of, and at the end of treatment. Images obtained with this protocol largely agree with postmortem studies of clubfeet. All of the major chondroosseous pathology could be visualized in vivo. With Ponseti treatment, all the abnormalities seen on the initial scans either improved markedly or corrected completely. Treatment resulted in correction not only of the abnormal relationships of the tarsal bones, but also of the abnormal shapes of the individual tarsal osteochondral anlages, probably because of the changes in growth resulting from the changes in mechanical loading of fast-growing tissues.

Myelodysplasia-like syndrome and end-stage liver disease: report of 2 cases.

We report 2 cases of myelodysplastic syndrome associated with cirrhosis caused by primary biliary cirrhosis and alpha1-antitrypsin deficiency. The etiology of myelodysplasia and its implication in liver transplantation is discussed.

Improved vascular tissue fusion using new light-activated surgical adhesive on a canine model.

Newly developed light-activated surgical adhesives have been investigated as a substitute to traditional protein solders for vascular tissue fusion without the need for sutures. Canine femoral arteries (n = 14), femoral veins (n = 14), and carotid arteries (n = 10) were exposed, and a 0.3-0.6 cm longitudinal incision was made in the vessel walls. The surgical adhesive, composed of a poly(L-lactic-co-glycolic acid) scaffold doped with the traditional protein solder mix of bovine serum albumin and indocyanine green dye, was used to close the incisions in conjunction with an 805 nm diode laser. Blood flow was restored to the vessels immediately after the procedure and the incision sites were checked for patency. The new adhesives were flexible enough to be wrapped around the vessels while their solid nature avoided the problems associated with "runaway" of the less viscous liquid protein solders widely used by researchers. Assessment parameters included measurement of the ex vivo intraluminal bursting pressure 1-2 h after surgery, as well as histology. The acute intraluminal bursting pressures were significantly higher in the laser-solder group (>300 mmHg) compared to the suture control group (<150 mmHg) where four evenly spaced sutures were used to repair the vessel (n = 4). Histological analysis showed negligible evidence of collateral thermal damage to the underlying tissue in the laser-solder repair group. These initial results indicated that laser-assisted vascular repair using the new adhesives is safe, easy to perform, and contrary to conventional suturing, provides an immediate leak-free closure. In addition, the flexible and moldable nature of the new adhesives should allow them to be tailored to a wide range of tissue geometries, thus greatly improving the clinical applicability of laser-assisted tissue repair.

Comparison of the Moskowitz criteria and the pouchitis disease activity index (PDAI) for diagnosis of ileoanal pouch inflammation.

OBJECTIVE: To prospectively compare two indices for diagnosis of pouchitis: Moskowitz criteria and pouchitis disease activity index (PDAI). PATIENTS AND METHODS: Fifty-six consecutive patients with an ileoanal pouch for ulcerative colitis were recruited. A clinical questionnaire was composed and the Oresland functional score calculated. Pouchoscopy and biopsy were performed after cleansing of the pouch. RESULTS: Seven patients had pouchitis according to both Moskowitz and PDAI ('positive' group). Five patients had PDAI > or = 7, but did not fulfil the Moskowitz criteria ('negative' group). The pouchoscopy and Oresland functional scores were similar between the two groups. The biopsy neutrophilia and ulceration were more prominent in the 'positive' group (chi2=5.18, P < 0.05), whereas urgency (chi2=8.4, P < 0.001), evacuation difficulties (chi2=5.18, P < 0.05) and history of bleeding per pouch (chi2=4.18, P < 0.05) were more pronounced in the 'negative' group. CONCLUSION: Moskowitz criteria may be broadly in agreement with the PDAI; these, however, cannot be regarded as interchangeable.

The effects of ethylene, depressed oxygen and elevated carbon dioxide on antioxidant profiles of senescing spinach leaves.

It has been suggested that antioxidants play a role in regulating or modulating senescence dynamics of plant tissues. Ethylene has been shown to promote early plant senescence while controlled atmospheres (CA; reduced O2 levels and elevated CO2 levels) can delay its onset and/or severity. In order to examine the possible importance of various antioxidants in the regulation of senescence, detached spinach (Spinacia oleracea L.) leaves were stored for 35 d at 10 degrees C in one of three different atmospheres: (1) ambient air (0.3% CO2, 21.5% O2, 78.5% N2), (2) ambient air + 10 ppm ethylene to promote senescence, or (3) CA (10% CO2, 0.8% O2 and 89.2% N2) to delay senescence. At weekly intervals, material was assessed for activities of the antioxidant enzymes ascorbate peroxidase (ASPX; EC 1.11.1.11), catalase (CAT; EC 1.11.1.6), dehydroascorbate reductase (DHAR; EC 1.8.5.4), glutathione reductase (GR; EC 1.6.4.2), monodehydroascorbate reductase (MDHAR; EC 1.6.5.4), and superoxide dismutase (SOD; EC 1.15.1.1), and concentrations of the water-soluble antioxidant compounds ascorbate and glutathione. Indicators of the rate and severity of senescence (lipid peroxidation, chlorophyll, and soluble protein levels) were also determined. Results indicated that the rate and severity of senescence was similar between the leaves stored in ambient air or CA until day 35, at which point the ambient air-stored leaves exhibited a sharp increase in lipid peroxidation. Tissues under both storage regimes demonstrated significant declines only in levels of ASPX, CAT, and ascorbate. Glutathione content in the CA-stored tissue also significantly dropped, but only on day 35. In contrast, spinach leaves stored in ambient air + ethylene experienced a rapid decrease in levels of all the antioxidants assessed except SOD. Declines in levels of ASPX, CAT, and ascorbate over the 35 d storage period regardless of the composition of the storage atmosphere suggests that regulation of H2O2 levels plays an important role in both the dynamics and severity of post-harvest senescence of spinach.

Luminal neutrophil migration in ileoanal pouches studied by whole gut lavage.

OBJECTIVE: White cell scintigraphy has shown that neutrophils migrate into the gut wall and lumen in ileoanal pouches. We aimed to establish whether whole gut lavage fluid can be used to investigate intestinal neutrophil migration in ileoanal pouches. DESIGN: A prospective single centre study recruiting consecutive patients. METHODS: Whole gut lavage with polyethylene glycol electrolyte solution was performed in 56 (32 men, 24 women) ileoanal pouch patients who had undergone colectomy for ulcerative colitis; the first clear effluent was collected, processed and stored at -70 degrees C. The fluid was assayed for neutrophil granulocyte elastase using a specific colorimetric assay, IgG, albumin, alpha1-antitrypsin, haemoglobin and cytokines IL-1beta and IL-8 using previously described techniques. Patients' disease activity was characterized following pouchoscopy and biopsy. RESULTS: Patients with pouchitis had significantly higher levels of granulocyte elastase in whole gut lavage fluid compared with those without pouchitis. Patients with detectable granulocyte elastase had higher pouchoscopy score, more severe mucosal neutrophil infiltration and protein loss and bleeding. These patients had significantly higher levels of cytokines IL-1beta and IL-8 in the whole gut lavage fluid, compared with patients with undetectable granulocyte elastase. CONCLUSION: Whole gut lavage fluid samples may provide a useful investigative tool to study mucosal inflammation and luminal neutrophil migration in ileoanal pouches.

Immunoglobulin G and albumin levels in whole gut lavage fluid provide an objective measure of pouch ileitis.

BACKGROUND: Gut protein loss is a characteristic of inflammatory bowel disease (IBD), and immunoglobulin (Ig) G, albumin and alpha1-antitrypsin concentrations in whole gut lavage fluid (WGLF) correlate with clinical disease activity. If inflammation in ileoanal pouches is similar to IBD, then measurement of protein-losing enteropathy by analysis of WGLF may provide an objective assessment of disease activity in pouches. METHODS: Forty-two patients who had restorative proctocolectomy for ulcerative colitis underwent whole gut lavage with a polyethylene glycol-electrolyte solution. The first clear effluent was filtered, processed by the addition of protease inhibitors and stored at - 70 degrees C. IgG, albumin and alpha1-antitrypsin were assayed in WGLF. The Pouchitis Disease Activity Index (PDAI) was calculated after pouchoscopy and biopsy; the Moskowitz criteria for pouchitis were also applied. RESULTS: There was a significant correlation of the pouchoscopy score and the PDAI with the concentration of WGLF IgG. All patients with 'pouchitis' according to the Moskowitz criteria had a WGLF IgG concentration greater than 10 microg/ml. The WGLF albumin level also showed a significant correlation with the PDAI, but alpha1-antitrypsin concentration did not. CONCLUSION: Analysis of WGLF for IgG and albumin may be useful in the assessment of disease activity in pouch inflammation.

The role of evolutionarily conserved sequences in alternative splicing at the 3' end of Drosophila melanogaster myosin heavy chain RNA.

Exon 18 of the muscle myosin heavy chain gene (Mhc) of Drosophila melanogaster is excluded from larval transcripts but included in most adult transcripts. To identify cis-acting elements regulating this alternative RNA splicing, we sequenced the 3' end of Mhc from the distantly related species D. virilis. Three noncoding regions are conserved: (1) the nonconsensus splice junctions at either end of exon 18; (2) exon 18 itself; and (3) a 30-nucleotide, pyrimidine-rich sequence located about 40 nt upstream of the 3' splice site of exon 18. We generated transgenic flies expressing Mhc mini-genes designed to test the function of these regions. Improvement of both splice sites of adult-specific exon 18 toward the consensus sequence switches the splicing pattern to include exon 18 in all larval transcripts. Thus nonconsensus splice junctions are critical to stage-specific exclusion of this exon. Deletion of nearly all of exon 18 does not affect stage-specific utilization. However, splicing of transcripts lacking the conserved pyrimidine sequence is severely disrupted in adults. Disruption is not rescued by insertion of a different polypyrimidine tract, suggesting that the conserved pyrimidine-rich sequence interacts with tissue-specific splicing factors to activate utilization of the poor splice sites of exon 18 in adult muscle.