Mechanisms of negative differential resistance in glutamine-functionalized WS2quantum dots

Understanding the mechanism of the negative differential resistance (NDR) in transition metal dichalcogenides is essential for fundamental science and the development of electronic devices. Here, the NDR of the current-voltage characteristics was observed based on the glutamine-functionalized WS₂quantum dots (QDs). The NDR effect can be adjusted by varying the applied voltage range, air pressure, surrounding gases, and relative humidity. A peak-to-valley current ratio as high as 6.3 has been achieved at room temperature. Carrier trapping induced by water molecules was suggested to be responsible for the mechanism of the NDR in the glutamine-functionalized WS₂QDs. Investigating the NDR of WS₂QDs may promote the development of memory applications and emerging devices.

Exercise, Processing Speed, and Subsequent Falls: A Secondary Analysis of a 12-Month Randomized Controlled Trial

BACKGROUND

Strength and balance retraining exercises reduce the rate of subsequent falls in community-dwelling older adults who have previously fallen. Exercise can also improve cognitive function, including processing speed. Given processing speed predicts subsequent falls, we aimed to determine whether improved processing speed mediated the effects of the Otago Exercise Program on the rate of subsequent: (i) total falls, (ii) non-injurious falls, (iii) moderate injurious falls, and (iv) serious injurious falls.

METHOD

A secondary complete case analysis of a 12-month, single-blind, randomized clinical trial among 256 of 344 adults aged at least 70 years who fell in the previous 12 months. Participants were randomized 1:1 to receive usual care plus the Otago Exercise Program (n = 123) or usual care (n = 133), consisting of fall prevention care provided by a geriatrician. The primary outcome was self-reported number of falls over 12 months (ie, rate of falls). Processing speed was assessed at baseline and at 12 months by the Digit Symbol Substitution Test (DSST). Causal mediation analyses were conducted using quasi-Bayesian estimates and 95% confidence intervals.

RESULTS

Exercise significantly reduced the rate of subsequent moderate injurious falls (IRR = 0.49; 95% CI: 0.31, 0.77; p = .002) and improved processing speed (estimated mean difference: 1.16 points; 95% CI: 0.11, 2.21). Improved DSST mediated the effect of exercise on the rate of subsequent moderate injurious falls (estimate: -0.06; 95% CI: -0.15, -0.001; p = .036).

CONCLUSION

Improved processing speed may be a mechanism by which exercise reduces subsequent moderate injurious falls in older adults who fell previously.

CLINICAL TRIALS REGISTRATION NUMBER

ClinicalTrials.gov Protocol Registration System:NCT01029171: https://clinicaltrials.gov/ct2/show/NCT01029171NCT00323596: https://clinicaltrials.gov/ct2/show/NCT00323596.

Lead-free cesium tin halide nanocrystals for light-emitting diodes and color down conversion

Organometal halide perovskites are attracting a great deal of attention because of their long carrier diffusion lengths, wide wavelength tunability, and narrow-band emission. However, the toxicity of lead has caused considerable environmental and health concerns. In this work, lead-free cesium tin halide nanocrystals are synthesized and investigated. CsSnBr3 and CsSnI3 nanocrystals, 25 and 7 nm in size, are synthesized by a facile hot injection method. Absorption spectroscopy, photoluminescence spectroscopy, and X-ray diffraction were used to understand their structural and optical properties. CsSnBr3 and CsSnI3 nanocrystals show emission peaks at 683 and 938 nm, respectively. These nanocrystals show shelf stability for a few months. Temperature-dependent photoluminescence is utilized to know more about fundamental physical parameters, such as exciton binding energy, charge carrier-phonon interactions and band gap. Light-emitting diodes and color down-conversion films are also demonstrated using these lead free perovskite nanocrystals.

Origins of the s-shape characteristic in J-V curve of inverted-type perovskite solar cells

Fullerene derivative thin films have been widely used in inverted-type perovskite solar cells as the electron transport layer (ETL) and hole blocking layer. However, the smooth contact at the interface between the hydrophobic [6,6]-phenyl-C₆₁-butyric acid methyl ester (PCBM) and hydrophilic CH₃NH₃PbI₃ (MAPbI₃) thin film has not yet been completely understood. The contact at the PCBM/MAPbI₃ interface strongly influences the photovoltaic performance. The photovoltaic devices were characterized by measuring the light intensity-dependent current density-voltage (J-V) curves and impedance spectra, which show that the contact at the PCBM/MAPbI₃ interface simultaneously influences the shunt resistance (carrier recombination) and series resistance (interfacial contact). In addition, x-ray diffraction patterns, atomic force microscopic images, absorbance spectra and photoluminescence spectra were used to explore the contact at the PCBM/MAPbI₃ interface. The experimental results show that the flat MAPbI₃ thin film cannot be completely covered by a PCBM thin film and thereby results in the s-shape characteristic in the J-V curve of the resultant solar cells. The s-shaped J-V curve can be suppressed by increasing the crystallinity and surface roughness of the MAPbI₃ thin film. With the use of an interface modification layer in between the PCBM thin film and Ag cathode, the power conversion efficiency of MAPbI₃ solar cells can be increased from 10.50% to 13.71%.

Bright and fast-response perovskite light-emitting diodes with an ICBA:modified-C60 nanocomposite electrical confinement layer

Bright and fast-response CH₃NH₃PbBr₃ perovskite light-emitting diodes (PeLEDs) are realized by using ICBA:modified C₆₀ (MC₆₀) nanocomposites as the hole blocking layer (HBL) and electron transport layer (ETL). The photoluminescence spectrum shows that the use of hydrophilic MC₆₀ in the ETL helps the surface passivation of the perovskite layer. In addition, the photoelectron spectra and water-droplet contact angle images show that the use of the ICBA:MC₆₀ nanocomposite ETL can simultaneously confine the electrons and holes in the perovskite layer, which boosts the injected electron-hole radiative recombination efficiency and thereby increases the electroluminescence from 1 cd m^-2 to 2080 cd m^-2 at 6 V when the ICBA:3,5OEC₆₀ nanocomposite ETL is used. In addition, the operational frequency of the optimal PeLED is up to 1.5 MHz.

Ultrastable, Deformable, and Stretchable Luminescent Organic-Inorganic Perovskite Nanocrystal-Polymer Composites for 3D Printing and White Light-Emitting Diodes

Organic-inorganic perovskite nanocrystals with excellent optoelectronic properties have been utilized in various applications, despite their stability issues. The perovskite materials are sensitive to environments such as polar solvents, moisture, and heat. Thus, they are not used for extrusion three-dimensional (3D) printing, as it is usually conducted in the ambient environment and requires heating to liquefy the printed materials. In this work, 11 thermoplastic polymers conventionally used for extrusion 3D printing were investigated to test their capability as protective encapsulation materials for perovskite nanocrystals. Three of them exhibited good protective properties, and one (polycaprolactone, PCL) of these three could be blended with perovskite nanocrystals to form perovskite nanocrystal-PCL composites, which were deformable and stretchable once heated. Because of the low melting point of PCL, the perovskite nanocrystals maintained their optical properties after 3D printing, and the printed objects were still having fluorescent behavior. Moreover, fluorescent micrometer-sized fibers based on the perovskite nanocrystal-PCL composites could also be simply prepared using cotton candy makers. Perovskite nanocrystal-PCL composite films with different emission wavelengths were incorporated with blue light-emitting diodes (LEDs) to realize white LEDs with Commission Internationale de l'Éclairage chromaticity coordinates of (0.33, 0.33).

Cognitive status is a determinant of health resource utilization among individuals with a history of falls: a 12-month prospective cohort study

SUMMARY

Falls are a costly public health problem worldwide. The literature is devoid of prospective data that identifies factors among fallers that significantly drive health care resource utilization. We found that cognitive function--specifically, executive functions--and cognitive status are significant determinants of health resource utilization among older fallers.

INTRODUCTION

Although falls are costly, there are no prospective data examining factors among fallers that drive health care resource utilization. We identified key determinants of health resource utilization (HRU) at 6 and 12 months among older adults with a history of falls. Specifically, with the increasing recognition that cognitive impairment is associated with increased falls risk, we investigated cognition as a potential driver of health resource utilization.

METHODS

This 12-month prospective cohort study at the Vancouver Falls Prevention Clinic (n = 319) included participants with a history of at least one fall in the previous 12 months. Based on their cognitive status, participants were divided into two groups: (1) no mild cognitive impairment (MCI) and (2) MCI. We constructed two linear regression models with HRU at 6 and 12 months as the dependent variables for each model, respectively. Predictors relating to mobility, global cognition, executive functions, and cognitive status (MCI versus no MCI) were examined. Age, sex, comorbidities, depression status, and activities of daily living were included regardless of statistical significance.

RESULTS

Global cognition, comorbidities, working memory, and cognitive status (MCI versus no MCI ascertained using the Montreal Cognitive Assessment (MoCA)) were significant determinants of total HRU at 6 months. The number of medical comorbidities and global cognition were significant determinants of total HRU at 12 months.

CONCLUSION

MCI status was a determinant of HRU at 6 months among older adults with a history of falls. As such, efforts to minimize health care resource use related to falls, it is important to tailor future interventions to be effective for people with MCI who fall.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT01022866.

A Facile and Low-Cost Method to Enhance the Internal Quantum Yield and External Light-Extraction Efficiency for Flexible Light-Emitting Carbon-Dot Films

Solution-processed, non-toxic carbon dots (CDs) have attracted much attention due to their unique photoluminescence (PL) properties. They are promising emissive layers for flexible light-emitting devices. To this end, the CDs in pristine aqueous solutions need to be transferred to form solid-state thin films without sacrificing their original PL characteristics. Unfortunately, solid-state PL quenching induced by extra non-radiative (NR) energy transfer among CDs would significantly hinder their practical applications in optoelectronics. Here, a facile, low-cost and effective method has been utilized to fabricate high-performance CD/polymer light-emitting flexible films with submicron-structured patterns. The patterned polymers can serve as a solid matrix to disperse and passivate CDs, thus achieving high internal quantum yields of 61%. In addition, they can act as an out-coupler to mitigate the waveguide-mode losses, approximately doubling the external light-extraction efficiency. Such CD/polymer composites also exhibit good photo-stability, and thus can be used as eco-friendly, low-cost phosphors for solid-state lighting.

A fixed denture for a child with epidermolysis bullosa simplex

AIM

To report the caries treatment and delivery of a fixed denture for a 3-year-old girl with epidermolysis bullosa simplex (EBS).

CASE REPORT

EBS is manifested on the skin or mucous membranes where skin separation is easily induced by trauma. Full- mouth rehabilitation under in-patient general anaesthesia was performed to the patient in conjunction with proper pre- and postoperative care. A fixed denture was fabricated and installed to replace the extracted teeth without later causing irritation on the mucosa. The prosthesis restored aesthetics and provided comfort without imposing the burden of compliance on the patient.

CONCLUSION

Aided by meticulous pre- and postoperative care and oral hygiene reinforcement, comprehensive dental treatment coupled with fixed denture delivery can greatly improve the life quality and aesthetics for children with EBS.

Prognostic value of oxygen consumption and ventilatory equivalent slope in female candidates referred for heart transplantation--experience of a single Asian center

BACKGROUND

Ventilatory equivalent (ventilation/CO2 production, VE/VCO2) slope has been suggested to be a much more accurate predicator than peak oxygen consumption (VO2) during exercise for prognosis in patients with heart failure. However, patients tested were predominately male.

METHODS

To investigate whether peak VO2 and VE/VCO2 slope predict the prognosis of female patients with heart failure, we retrospectively collected data of 39 female candidates referred for heart transplantation (HTx) from 2004 to 2011. Both peak VO2 and VE/VCO2 slope were obtained from the results of an exercise pulmonary function test. The outcome was death or mechanical devices implantation or HTx. Logistic regression was used for data analysis.

RESULTS

Mean age and heart failure survival score were 55.8 ± 13.7 years and 7.3 ± 0.7, respectively. Each increment of VE/VCO2 slope decreased 2-year event-free rate (odds ratio [OR] = 0.88, 95% confidence interval [CI] = 0.79 to 0.98) in the female group. The predictions of VE/VCO2 slope for 1-year event-free survival did not reach statistical significance (OR = 0.92, 95% CI = 0.84 to 1.00). On the other hand, peak VO2 was not a strong predictor for 1- and 2-year event-free survival (OR = 1.22 and 1.16, 95% CI = 0.96 to 1.55 and 0.94 to 1.44, respectively).

CONCLUSIONS

Impairment in exercise ventilation holds a clinical and long-term prognostic impact in female patients with heart failure. The role of peak VO2 during exercise in prognostic prediction among the cohort should be further investigated.

Movement of entomophagous arthropods in agricultural landscapes: links to pest suppression

Entomophagous arthropods can provide valuable biological control services, but they need to fulfill their life cycle in agricultural landscapes often dominated by ephemeral and disturbed habitats. In this environment, movement is critical to escape from disturbances and to find resources scattered in space and time. Despite considerable research effort in documenting species movement and spatial distribution patterns, the quantification of arthropod movement has been hampered by their small size and the variety of modes of movement that can result in redistribution at different spatial scales. In addition, insight into how movement influences in-field population processes and the associated biocontrol services is limited because emigration and immigration are often confounded with local-scale population processes. More detailed measurements of the habitat functionality and movement processes are needed to better understand the interactions between species movement traits, disturbances, the landscape context, and the potential for entomophagous arthropods to suppress economically important pests.

Limits on spin-independent couplings of WIMP dark matter with a p-type point-contact germanium detector

We report new limits on a spin-independent weakly interacting massive particle (WIMP)-nucleon interaction cross section using 39.5 kg days of data taken with a p-type point-contact germanium detector of 840 g fiducial mass at the Kuo-Sheng Reactor Neutrino Laboratory. Crucial to this study is the understanding of the selection procedures and, in particular, the bulk-surface events differentiation at the sub-keV range. The signal-retaining and background-rejecting efficiencies were measured with calibration gamma sources and a novel n-type point-contact germanium detector. Part of the parameter space in the cross section versus WIMP-mass implied by various experiments is probed and excluded.

Examining the relationship between specific cognitive processes and falls risk in older adults: a systematic review

This systematic review aims to establish which cognitive domains are associated with falls or falls risk. Recent evidence suggests that impaired cognition increases seniors' risk of falling. The purpose of this review was to identify the cognitive domains that are significantly associated with falls or falls risk in older adults. We conducted a systematic review of peer-reviewed journal articles published from 1948 to present, focusing on studies investigating different domains of cognitive function and their association with falls or falls risk in adults aged 60 years or older. In accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines, we completed a comprehensive search of MEDLINE, PubMed, and EMBASE databases to identify studies examining the association between cognitive function and falls or falls risk. With an expert in the field, we developed a quality assessment questionnaire to rate the quality of the studies included in this systematic review. Twenty-five studies were included in the review. We categorized studies based on two related but distinct cognitive domains: (1) executive functions or (2) dual-task ability. Twelve studies reported a significant association between executive functions and falls risk. Thirteen studies reported that dual-task performance is a predictor of falls or falls risk in older adults. Three studies did not report an association between cognition and falls risk. Consistent evidence demonstrated that executive functions and dual-task performance were highly associated with falls or falls risk. The results from this review will aid healthcare professionals and researchers in developing innovative screening and treatment strategies for mitigating falls risk by targeting specific cognitive domains.

A comparative study of loratadine syrup and cyproheptadine HCL solution for treating perennial allergic rhinitis in Taiwanese children aged 2-12 years

We assessed the efficacy of loratadine syrup compared with cyproheptadine HCl solution for treating children aged from 2 to 12 years with perennial allergic rhinitis (PAR) in Taiwan. Sixty children with mite-induced PAR were enrolled and randomly placed into two treatment groups: loratadine syrup or cyproheptadine HCl solution. Treatment efficacy and symptom changes from baseline to post-treatment were evaluated by total symptom scores and visual analogue scales (VAS) during a 2-week period. There were no differences in age, gender, height, or weight between the two groups. After 2 weeks of treatment, there was a significantly greater reduction in symptom scores in the loratadine group than in the cyproheptadine group (p<0.001). Clinical and subjective VAS showed significant differences in percentage changes from baseline between the loratadine and cyproheptadine groups at all time points (all p<0.001, in favor of loratadine). Clinical VAS change at week 1: 95.1 vs 11.3; subjective VAS change at week 1: 88.6 vs 13.6; clinical VAS change at week 2: 125.5 vs 18.3; subjective VAS change at week 2: 101.4 vs 7.1. Thus, loratadine was superior to cyproheptadine for alleviating both nasal and non-nasal symptoms of perennial allergic rhinitis in Taiwanese children aged 2-12 years.

A ZnO-nanowire phototransistor prepared on glass substrates

The fabrication of a phototransistor via the bridging of two prefabricated electrodes with a laterally grown ZnO nanowire is reported. It was found that the fabricated device is an n-channel enhancement-mode phototransistor with a dark carrier concentration of 6.34 × 10(17) cm(-3) when the gate voltage is biased at 5 V. With an incident-light wavelength of 360 nm and a zero gate bias, it was found that the noise equivalent power and normalized detectivity (D*) of the fabricated ZnO phototransistor were 6.67 × 10(-17) W and 1.27 × 10(13) cm Hz(0.5) W(-1), respectively. It was also found that the current in the device can be modulated efficiently by tuning the wavelength of the excitation source.

Edge effects in the directionally biased distribution of Choristoneura rosaceana (Lepidoptera: Tortricidae) in apple orchards

Edge effect tests have been used in a number of studies on obliquebanded leafroller, Choristoneura rosaceana (Harris), to test for evidence of mated female immigration into pheromone-treated orchards. This type of test compares obliquebanded leafroller presence or activity around the perimeter of an orchard against presence or activity in the interior. Higher numbers detected around the edges of an orchard would indicate higher levels of flight activity at the edge, a pattern that could be generated by high levels of immigration. Recent work has shown that the spatial distribution of recaptured obliquebanded leafroller adults released from a single location can be directionally biased, which could obscure the ability to detect an edge effect. To test this theory, data from an orchard study conducted in 1991 that found no significant edge effect was reanalyzed. When we accounted for the directional bias in the distribution of first-generation mated female moths, we found an edge effect with significantly more mated females captured in the edge traps than in the center or mid-interior traps. No edge effect was found when the directional bias was ignored. In addition, second-generation males and mated females both showed a significant edge effect that had not been detected in the original analysis, which had combined both first- and second-generation data.

Bromism caused by mix-formulated analgesic injectables

Bromism, chronic bromide intoxication, can be caused by a variety of medicines, but bromism due to pain-relieving injectable medications has not been reported. In this study, the methods used were internet searching on bromide-containing injectables available in Taiwan and the first case report of bromism due to mixed-formulated injectable medication. Many analgesic/antipyretic and antihistamine injections containing bromides are still being used in Taiwan. They contain sodium bromide up to 1000 mg/ampoule or calcium bromide up to 800 mg/amp. A 25-year-old female suffered from forgetfulness and unstable gait after long-term frequent injections of a preparation to relieve head and neck pain. Blood tests showed hyperchloremia (171 mEq/L) and a negative anion gap (-48.7 mEq/L). Serum bromide measured 2150 mg/L. She recovered completely in 3 days with saline treatment. Many bromide-containing injections are still being used in Taiwan. Clinicians should keep alert on this issue to avoid iatrogenic bromism or making misdiagnoses.

Galectin-1, a novel ligand of neuropilin-1, activates VEGFR-2 signaling and modulates the migration of vascular endothelial cells

Galectin-1 (Gal-1), a homodimeric prototype of the galectins with a single carbohydrate-recognition domain, was recently identified as being overexpressed in tumor-associated capillary endothelial cells. The role of Gal-1 in endothelial cellular functions and the mechanism of action of Gal-1 remain unknown. Neuropilin-1 (NRP1) is a neuronal receptor that mediates repulsive growth cone guidance, and NRP1 functions in endothelial cells as a coreceptor (with vascular endothelial growth factor receptors (VEGFRs)) for VEGF(165). In this study, we found that Gal-1 was overexpressed in the tumor-associated endothelial cells of oral squamous cell carcinomas (P<0.001). Gal-1 increased the proliferation and adhesion of endothelial cells, and enhanced cell migration in combination with VEGF(165). Surprisingly, Gal-1 selectively bound NRP1 via the carbohydrate-recognition domain, but did not bind VEGFR-1, VEGFR-2 or VEGFR-3. The Gal-1-NRP1 interaction mediated the migration and adhesion of endothelial cells. The binding of Gal-1 to NRP1 enhanced VEGFR-2 phosphorylation and stimulated the activation of the mitogen activated protein (MAP) kinases SAPK1/JNK (stress activated protein kinase-1/c-Jun NH2-terminal kinase). These findings show, for the first time, that Gal-1 can directly bind to NRP1 on endothelial cells, and can promote the NRP1/VEGFR-2-mediated signaling pathway as well as NRP1-mediated biological activities.

Impaired exercise capacity in diabetic patients after coronary bypass surgery: effects of diastolic and endothelial function

OBJECTIVES

The aims of this study were to clarify the influence of cardiac diastolic and peripheral vascular function on the exercise capacity of patients with coronary bypass surgery (CABG) and diabetes mellitus (DM) by tissue Doppler imaging (TDI) and flow-mediated vasodilatation (FMD), and to investigate interrelations between exercise capacity and LV diastolic function, endothelial function and biochemical parameters.

METHODS

We analyzed the exercise capacity, TDI at the mitral annulus and FMD in 51 uncomplicated first-time CABG survivors (23 DM) at an average interval of 21.6 +/- 12.2 months after surgery.

RESULTS

Diabetics had lower E', A', VO(2)peak, (a-v)O(2) difference, and higher E/E' ratios (p < 0.05) than non-DM patients, but not FMD (p = 0.17). The A and E/E' ratios correlated negatively with VO(2)peak after age adjustment (r = -0.336, p = 0.024). In addition, HbA(1c), and triglyceride also correlated negatively with VO(2)peak (r = -0.377, -0.307, respectively, p < 0.05).

CONCLUSIONS

Diabetics after CABG had more advanced diastolic dysfunction and oxygen extraction impairment than non-DM. It suggests these factors could contribute to lower exercise capacity, risk of developing heart failure despite preserved systolic function and poorer long-term survival of diabetic patients after CABG.

The effect of residual chemical oxygen demand on anoxic and aerobic phosphate uptake and release with various intracellular polymer levels

This study investigated the anoxic and aerobic phosphate uptake and release reactions and the fraction of denitrifying phosphate-accumulating organisms (DPAOs) under various initial chemical oxygen demand (COD) and residual COD conditions. The results showed that DPAOs and non-DPAOs could release phosphate when high soluble COD was present. Consequently, the phosphate-uptake potential was dynamic and increased when the initial COD increased, the initial polyhydroxyalkanoates (PHA) increased, and the residual COD decreased. Furthermore, the electron acceptor (oxygen of nitrate) has more significant influence on the phosphate uptake/release characteristics, while the residual COD concentrations have little influence on that. The fraction of DPAOs to phosphate-accumulating organisms was 42% when the initial PHA storage was enough by both DPAOs and non-DPAOs. This was closely related to the relative phosphate uptake (47%) in the anoxic zone of the process.

Nitrification efficiency and nitrifying bacteria abundance in combined AS-RBC and A2O systems

This study makes a comparison between the nitrification performance of TNCU-I (a combined activated sludge-rotating biological contactor process) and A2O systems by the use of a pilot plant and batch experiments. The nitrifier abundance in both systems was determined, using cloning-denaturing gradient gel electrophoresis (DGGE) and fluorescent in-situ hybridization (FISH), to investigate the role of rotating biological contactor in the TNCU-I process. The stability of the nitrification performance and the specific nitrification rate were found to be greater in TNCU-I system than in the A2O system. RBC biofilm promoted nitrifying activity that contributed to the nitrification performance, especially at a low SRT. By using the cloning-DGGE method, the genera Nitrosospira and Nitrospira were found to be present in all the samples, while the genus Nitrosomonas was observed only in the TNCU-I RBC biofilm. In addition, the proportions of ammonia oxidizer in the TNCU-I RBC biofilm, the TNCU-I activated sludge and the A2O activated sludge were 11.4%, 13.2%, and 4.1%, respectively, higher than the nitrite oxidizer fractions of 3.3%, 5.7% and 2.1%, respectively, according to the cloning-DGGE method. On the other hand, the proportions of ammonia oxidizers in the afore-mention materials were 10.3%, 13.7%, and 5.2%, higher than the nitrite oxidizer fractions of 2.5%, 3.6% and 2.3%, according to the FISH experiments. This implies that the proportion of ammonia oxidizer in the TNCU-I process was 3.2 and 2.6 times that in the A2O process, determined by the cloning-DGGE and FISH methods, respectively. These amounts are also close to the ammonia oxidization rate of 2.9 times. All the data show that RBC added to the aerobic zone of TNCU-I process would increase the nitrifier abundance and enhance the nitrification performance of the system.

Binding and partial denaturing of G-quartet DNA by Cdc13p of Saccharomyces cerevisiae

The protein Cdc13p binds telomeres in vivo and is essential for the maintenance of the telomeres of Saccharomyces cerevisiae. In addition, Cdc13p is known to bind single-stranded TG(1-3) DNA in vitro. Here we have shown that Cdc13p also binds DNA quadruplex, G-quartet, formed by TG(1-3) DNA. Moreover, the binding of Cdc13p causes a partial denaturing of the G-quartet DNA. Formation of DNA quadruplexes may involve the intermolecular association of TG(1-3) DNA and inhibit the extension of telomeres by telomerase. Thus, our finding suggests that Cdc13p may disrupt telomere association and facilitate telomere replication.

Identification and characterization of a novel androgen receptor coregulator ARA267-alpha in prostate cancer cells

The androgen receptor (AR) is a member of the steroid receptor superfamily that binds to the androgen response element to regulate target gene transcription. AR may need to interact with some selected coregulators for maximal or proper androgen function. Here we report the isolation of a new AR coregulator with a calculated molecular mass of 267 kDa named the androgen receptor-associated protein 267-alpha (ARA267-alpha). ARA267-alpha contains 2427 amino acids, including one Su(var)3-9, Enhancer-of-zeste, and Trithorax (SET) domain, two LXXLL motifs, three nuclear translocation signal (NLS) sequences, and four plant homeodomain (PHD) finger domains. Northern blot analyses reveal that ARA267-alpha is expressed predominantly in the lymph node as 13- and 10-kilobase transcripts. HepG2 is the only cell line tested that does not express ARA267-alpha. Yeast two-hybrid and glutathione S-transferase pull-down assays show that both the N and C terminus of ARA267-alpha interact with the AR DNA- and ligand-binding domains. Unlike other coregulators, such as CBP, which enhance the interaction between the N and C terminus of AR, we found that ARA267-alpha had little influence on the interaction between the N and C terminus of AR. Luciferase and chloramphenicol acetyltransferase assays show that ARA267-alpha can enhance AR transactivation in a dihydrotestosterone-dependent manner in PC-3 and H1299 cells. ARA267-alpha can also enhance AR transactivation with other coregulators, such as ARA24 or PCAF, a histone acetylase, in an additive manner. Together, our data demonstrate that ARA267-alpha is a new AR coregulator containing the SET domain with an exceptionally large molecular mass that can enhance AR transactivation in prostate cancer cells.

Specific binding of single-stranded telomeric DNA by Cdc13p of Saccharomyces cerevisiae

Cdc13p is a single strand telomere-binding protein of Saccharomyces cerevisiae; its telomere-binding region is within amino acids 451-693, Cdc13(451-693)p. In this study, we used purified Cdc13p and Cdc13(451-693)p to characterize their telomere binding activity. We found that the binding specificity of single-stranded TG(1-3) DNA by these two proteins is similar. However, the affinity of Cdc13(451-693)p to DNA was slightly lower than that of Cdc13p. The binding of telomeric DNA by these two proteins was disrupted at NaCl concentrations higher than 0.3 m, indicating that electrostatic interaction contributed significantly to the binding process. Because both proteins bound to strand TG(1-3) DNA positioned at the 3' end, the 5' end, or in the middle of the oligonucleotide substrates, our results indicated that the location of TG(1-3) in single-stranded DNA does not appear to be important for Cdc13p binding. Moreover, using DNase I footprint analysis, the structure of the telomeric DNA complexes of Cdc13p and Cdc13(451-693)p was analyzed. The DNase I footprints of these two proteins to three different telomeric DNA substrates were virtually identical, indicating that the telomere contact region of Cdc13p is within Cdc13(451-693)p. Together, the binding properties of Cdc13p and its binding domain support the theory that the specific binding of Cdc13p to telomeres is an important feature of telomeres that regulate telomerase access and/or differentiate natural telomeres from broken ends.

Renaturation and stabilization of the telomere-binding activity of Saccharomyces Cdc13(451-693)p by L-arginine

Production of recombinant proteins can be valuable in studying their biological functions. However, recombinant proteins expressed in Escherichia coli sometimes form undesirable insoluble aggregates. Solubilization and renaturation of these aggregates becomes a problem that one needs to solve. Here we used recombinant Cdc13(451-693)p as example to show the presence of l-arginine during renaturation greatly enhanced the renaturation efficiency. Cdc13p is the single-stranded telomere-binding protein of yeast Saccharomyces cerevisiae. The telomere-binding domain has been mapped within amino acids 451-693 of Cdc13p, Cdc13(451-693)p. Recombinant Cdc13(451-693)p was expressed in E. coli as insoluble protein aggregates. Purification of insoluble Cdc13(451-693)p was achieved by denaturing the protein with 6 M guanidine-HCl and followed by Ni-nitrilotriacetic acid agarose column chromatography. Renaturation of Cdc13(451-693)p to the active form was achieved by dialyzing denatured protein in the presence of l-arginine. Moreover, the presence of l-arginine was also helped in maintaining the telomere-binding activity of Cdc13(451-693)p. Taking together, l-arginine might have a general application in renaturation of insoluble aggregates.

Effects of flow velocity and paving material, on nitrogen transformations, in shallow open channels

A study was conducted to investigate the effects of the flow velocity and the paving material on the nitrogen conversion rates in shallow open channels. Equal amounts of hollow holed and plain balls, all with a 3.5-cm diameter, was fastened to the channel bottom. Then the nitrogen conversion rates were taken at various velocities and compared. The inner and outer surfaces of the holed ball channel were about 1.5 times than of the plain ball channel, but the attached biofilm mass was found to be about 3.55 times greater. The optimal nitrogen conversion rates were found to be higher in the holed ball channel. A suitable velocity was determined which would enhance the optimal nitrogen conversion rates. The choice of velocity and the biofilm carrier to enhance or predict the nitrogen transformations in shallow channels, should be considered in model development.

Construction of a tagging system for subcellular localization of proteins encoded by open reading frames

We have previously characterized a monoclonal antibody (SC1D7) that is directed to maltose-binding protein (MBP) of Escherichia coli and other closely related enteric bacteria. SC1D7 does not cross-react with proteins in eucaryotes and appears to be a highly specific tool in immunochemical analyses. To better map the epitope, we took advantage of an available plasmid, pMAL-c2, that encodes the E. coli MBP-coding sequence and constructed plasmids to express MBP fragments. A construct containing the N-terminal portion of MBP does not react with SC1D7, whereas a second construct expressing glutathione S-transferase fused with the C-terminal half of MBP does react with SC1D7. To precisely define the epitope, random peptides displayed on M13 were used to react with SC1D7. Sequences of reactive peptides were aligned, and a consensus sequence of XDXRIPX was deduced. This sequence matches MBP with an amino acid stretch of KDPRIAA. To consolidate the mapping result, a sequence encoding this epitope was inserted into an expression vector and the resulting recombinant protein did react with SC1D7. Thereafter, this epitope was incorporated into a eucaryotic expression plasmid containing a previously defined hepatitis delta virus epitope for protein tagging. This two-epitope-tagging vector is useful in various molecular analyses. We demonstrate its usage for localization of a bacterial virulence factor in host cells. This vector should be applicable for high-throughput characterization of new open reading frames found in genome sequencing.

Analysis for Giardia cysts and Cryptosporidium oocysts in water samples from small water systems in Taiwan

Giardia and Cryptosporidium have emerged as waterborne pathogens of concern. Twenty-six water samples were collected from small water systems in Taiwan and checked for the occurrence of both parasites. Water quality parameters and characteristics of the sampling sites were also recorded. The frequencies of occurrence for Giardia and Cryptosporidium were 46.2% for each; and their mean concentrations were 79.5 cysts/100 l and 22.1 oocysts/100 l, respectively. The concentrations of oocysts and heterotrophic bacteria exhibited the highest correlation and followed the concentrations of the two protozoa. The water samples from sites with filtration devices had a lower oocyst concentration than those from sites without filtration devices, while no significant difference was found for cysts. The level of each parasite had no direct relationship with altitude. The cyst concentrations increased proportionally with the consumer population using the water systems. Risk assessment of the parasitic infections suggests that setting up disinfection devices in the small water systems would be needed.

Evaluation of two concentration methods for detecting Giardia and Cryptosporidium in water

The cartridge filtration method and membrane filtration method based on the fluorescent antibody procedure were evaluated for their recovery efficiencies and detection limits of Giardia and Cryptosporidium. We assessed the performances of the two concentration methods for water samples collected from Taiwan water treatment plants. The membrane filtration method was characterized by higher recovery rate and detection limit comparing with the cartridge filtration method. The occurrences of both parasites, and the relationships of parasite concentrations with indicator microorganisms show inconsistency between the two methods. It was discovered that water turbidity reduced the recovery efficiencies, and raised the detection limits for both parasites regardless of the method used.

Functional analysis of androgen receptor N-terminal and ligand binding domain interacting coregulators in prostate cancer

Several new androgen receptor (AR) coregulators, including ARA70, ARA55, ARA54, ARA160 and ARA24, associated with the N-terminal or the ligand-binding domain (LBD) of AR, have been identified by our group. We first identified the AR-LBD coregulators ARA70, ARA55, and ARA54. Our previous reports suggest that ARA70 can enhance the androgenic activity of 17 beta-estradiol (E2) and antiandrogens toward AR. It is of interest to compare and determine if the specificity of sex hormones and antiandrogens can be modulated by different coregulators. Our results indicate that, ARA70 is the best coregulator for increasing the androgenic activity of E2. Only ARA70 and ARA55 were able to significantly increase the androgenic activity of hydroxyflutamide, the active metabolite of a widely-used antiandrogen for the treatment of prostate cancer. Furthermore, our results suggest that among the LBD coregulators, ARA70 has a relatively high specificity for AR in the human prostate cancer cell line DU145. Together, our data suggest that the androgenic activity of some sex hormones and antiandrogens can be modulated by selective AR coactivators. In addition to the AR-LBD associated proteins, ARA24 and ARA160 have been identified as AR coregulators, interacting with the AR N-terminal instead of the LBD. Functional analysis revealed that the AR N-terminal coregulator ARA160 could cooperate with the AR LBD-associated coregulator ARA70. Our data indicate that ARA24 could also interact with AR, and that this binding is decreased by an expanding poly-glutamine (Q) length within AR. The length of the poly-Q stretch in the AR N-terminal domain is inversely correlated with the transcriptional activity of AR. Our data suggest that optimal AR transactivation may require interaction of AR with AR coregulators. The identification of factors or peptides that can interrupt androgen-mediated AR-ARA interactions may be useful in the development of better antiandrogens for treating androgen-related diseases, such as prostate cancer.

Increase of androgen-induced cell death and androgen receptor transactivation by BRCA1 in prostate cancer cells

Although mutations of the breast cancer susceptibility gene 1 (BRCA1) may play important roles in breast and prostate cancers, the detailed mechanism linking the functions of BRCA1 to these two hormone-related tumors remains to be elucidated. Here, we report that BRCA1 interacts with androgen receptor (AR) and enhances AR target genes, such as p21((WAF1/CIP1)), that may result in the increase of androgen-induced cell death in prostate cancer cells. The BRCA1-enhanced AR transactivation can be further induced synergistically with AR coregulators, such as CBP, ARA55, and ARA70. Together, these data suggest that the BRCA1 may function as an AR coregulator and play positive roles in androgen-induced cell death in prostate cancer cells and other androgen/AR target organs.

The prevalence of Giardia and Cryptosporidium in Taiwan water supplies

Giardia and Cryptosporidium have emerged as waterborne pathogens of concern. Thirty-one water samples were collected from nine potable water treatment plants in Taiwan and investigated for the presence of Giardia cysts and Cryptosporidium oocysts. The immunofluorescence assay was used for the simultaneous detection of cysts and oocysts. The frequency of occurrence of cysts was 77.8% for Giardia and 72.2% for Cryptosporidium in 18 raw water samples. Ten out of 13 samples collected from treated water samples showed the presence of cysts, while in 5 out of 13 treated water samples oocysts were detected. The risk assessment for adverse human effects arising from the presence of cysts and oocysts indicates the possibility of waterborne transmission of Giardia and Cryptosporidium infection in Taiwan if water is not adequately treated.

Expression, crystallization and preliminary X-ray diffraction studies of N-carbamyl-D-amino-acid amidohydrolase from Agrobacterium radiobacter

The Agrobacterium radiobacter CCRC 14924 N-carbamyl-D-amino-acid amidohydrolase, the enzyme used for production of D-amino acids, was overexpressed in Escherichia coli JM109. The expressed protein was crystallized by vapour diffusion using lithium sulfate as precipitant. It crystallizes in space group P21 with unit-cell parameters a = 69.8, b = 67.9 and c = 137.8 A and beta = 96.4 degrees. There are four molecules per asymmetric unit. Crystals diffract to 2.8 A resolution using a rotating-anode source at cryogenic (113 K) temperatures.

Water balance, growth, development, and survival of arboreal frog eggs (Chirixalus eiffingeri, Rhacophoridae): importance of egg distribution in bamboo stumps

We studied the effects of substrate moisture and flooding on the arboreal eggs of Chirixalus eiffingeri and determined the possible causes of egg mortality. Eggs appear highly permeable to water vapor, losing 16.24% and 38.38% of initial egg mass in 2 h at 90% and 45% relative humidity, respectively. Eggs that experienced positive water uptake developed faster, hatched earlier with larger hatchlings, and had greater hatching success than eggs that experienced negligible or negative water uptake. The hatching success of eggs that were submerged in water in bamboo stumps was significantly lower than that of eggs that were incubated on the water surface and was significantly correlated with the water PO2. In some bamboo stumps, we observed chironomid and tipulid larvae preying on submerged eggs. A dilution of water collected from bamboo stumps did not increase the hatching success of eggs. The water PO2 of bamboo stumps in the field was 67.4+/-18.8 mmHg, and the degree of hypoxia of water in each bamboo stump was correlated with the turbidity. Our findings demonstrated that the vertical distribution of C. eiffingeri eggs on walls of bamboo stumps significantly influenced the growth, development, and survival of embryos. Eggs deposited too far from the water may become desiccated, while eggs deposited too close to the water may become submerged and die of hypoxia or predation by insect larvae.

Tumor promoting effect of N-nitroso-N-(2-hexanonyl)-3'-nitrotyramine (a nitrosated Maillard reaction product) in benzo(a)pyrene-initiated mouse skin carcinogenesis

N-nitroso-N-(2-hexanonyl)-3'-nitrotyramine (NO-HNTA) is a product generated in a model browning system in the presence of sodium nitrite. The chemical structure of this compound has been confirmed by UV, mass, nuclear magnetic resonance and infrared spectroscopy in our study. Twenty weeks, twice weekly, topical application of NO-HNTA at the concentration of 10, 50 and 250 mumol to mice previously initiated with benzo(a)pyrene (B[a]P) increased their tumor formation by 3.2-, 4.6- and 5.8-fold respectively. Application of the same amount of NO-HNTA not only caused significant induction of hyperplasia but also the activity of epidermal ornithine decarboxylase (ODC). Treatment of mouse skin with various amounts of NO-HNTA (10, 50 and 250 mumol) caused production of hydrogen peroxide by 1.38-, 1.95- and 3.26-fold respectively, and induction myeloperoxidase (MPO) by 24-, 63- and 102-fold. These results indicate that the formation of NO-HNTA or its derivatives derived from the reaction of tyrosine and glucose in the presence of sodium nitrite has the potential as a tumor promoter.

Hypopharyngeal carcinoma with clinical peritoneal carcinomatosis: a report of two patients

Most patients with hypopharyngeal carcinomas show advanced disease, either at the primary site or in the neck, at the time of diagnosis. Despite intensive therapy, a great number of recurrences and distant metastases can be observed. The most common metastatic sites are the lung and bone, and only in autopsy cases has peritoneum carcinomatosis been mentioned as a metastatic site. Since January 1992, two of 78 patients (2.3%) with advanced hypopharyngeal squamous cell carcinomas (SCCs) treated initially by chemotherapy in our department developed clinical peritoneal carcinomatosis during their natural courses. Both patients were man patients with advanced locoregional disease at stage T4N3. Their clinical peritoneal carcinomatosis appeared during chemotherapy, with good disease control above the clavicle. Both patients eventually died of sepsis within 1 month after diagnosis of the peritoneal carcinomatosis. The authors suggest that peritoneal carcinomatosis is not as rare as previously believed, and should be included in the differential diagnosis in patients with advanced hypopharyngeal SCC with abdominal symptoms. Peritoneal carcinomatosis appears to be refractory to chemotherapy, and carried a poor prognosis in patients in the present study.

Hepatocellular carcinoma presenting as jaundice, hemobilia, and acute pancreatitis: a case report

A 48-year-old asymptomatic male hepatitis B virus carrier presented with a 2-day history of fever, chills, right upper quadrant abdominal pain, and jaundice. Shock was detected on admission. Emergency abdominal computed tomography (CT) scanning without contrast enhancement showed the features of acute pancreatitis. Hemobilia, edematous pancreatitis, cholestasis and cholecystitis were found on exploratory laparotomy. Neither stone nor active bleeding were detected on intraoperative choledochoscopic examination. Postoperative T-tube cholangiography one month later revealed non-opacification of the left intrahepatic duct. The patient's abdominal pain and hemobilia recurred. Celiac angiography and CT scanning with contrast showed two hepatocellular carcinomas (HCC) in the left lobe of the liver. This is the first case report in the English literature of HCC presenting as jaundice, hemobilia, and acute pancreatitis.

Potential effect of sodium nitrite on the expression of nuclear proto-oncogenes during 2-acetyl aminofluorene-induced hepatocarcinogenesis in rats

2-acetyl aminofluorene (AAF) reacts in acidic conditions with nitrous fume yielding N-nitroso-AAF (N-NO-AAF), as previously described, that exerts more toxic and mutagenic effects than its parental compound. In this study, the effect of sodium nitrite (NaNO2) on the tumorigenicity of AAF in rats fed with AAF and NaNO2 was observed. Wistar rats were divided into five groups: group I served as control; group II were treated with NaNO2 (0.3%); group III was given 0.02% AAF alone; groups IV and V received both AAF and NaNO2 (0.2 and 0.3% respectively) in their diet for 12 weeks. At the end of the experiment, all rats in groups III, IV and V developed early stage phenomena of hepatocellular carcinoma, including hepatomegaly with variable-sized foci and neoplastic nodules. Severe damage was observed in the rats treated with AAF and NaNO2. Feeding of AAF (0.02%) for 3 months elevated the levels of c-Fos, c-Jun and c-Myc proteins in the rat livers. The AAF-induced c-Jun, c-Fos and c-Myc expressions were significantly magnified (P < 0.001) by NaNO2. These data confirmed that the strengthening of AAF-induced hepatocarcinogenesis by NaNO2 should be associated with its enhancing effect on the AAF-induced increases in the expressions of c-Jun, c-Fos and c-Myc.

A redundant nuclear protein binding site contributes to negative regulation of the mouse mammary tumor virus long terminal repeat

The tissue specificity of mouse mammary tumor virus (MMTV) expression is controlled by regulatory elements in the MMTV long terminal repeat (LTR). These regulatory elements include the hormone response element, located approximately between -200 and -75, as well as binding sites for NF-1, Oct-1 (OTF-1), and mammary gland enhancer factors. Naturally occurring MMTV deletion variants isolated from T-cell and kidney tumors, transgenic-mouse experiments with MMTV LTR deletions, and transient transfection assays with LTR constructs indicate that there are additional transcription regulatory elements, including a negative regulatory element (NRE), located upstream of the hormone response element. To further define this regulatory region, we have constructed a series of BAL 31 deletion mutants in the MMTV LTR for use in transient transfection assays. These assays indicated that deletion of two regions (referred to as promoter-distal and -proximal NREs) between -637 and -201 elevated basal MMTV promoter activity in the absence of glucocorticoids. The region between -637 and -264 was surveyed for the presence of nuclear protein binding sites by gel retardation assays. Only one type of protein complex (referred to as NRE-binding protein or NBP) bound exclusively to sites that mapped to the promoter-distal and -proximal NREs identified by BAL 31 mutations. The promoter-proximal binding site was mapped further by linker substitution mutations and transfection assays. Mutations that mapped to a region containing an inverted repeat beginning at -287 relative to the start of transcription elevated basal expression of a reporter gene driven by the MMTV LTR. A 59-bp DNA fragment from the distal NRE also bound the NBP complex. Gel retardation assays showed that mutations within both inverted repeats of the proximal NRE eliminated NBP binding and mutations within single repeats altered NBP binding. Intriguingly, the NBP complex was detected in extracts from T cells and lung cells but was absent from mammary gland cells. These results suggest that a factor contributing to high-level expression of MMTV in the mammary gland is the lack of negative regulation by NBP.

Assay of the enantiomers of ibutilide and artilide using solid-phase extraction, derivatization, and achiral-chiral column-switching high-performance liquid chromatography

Ibutilide fumarate and artilide fumarate, new drugs for the treatment of cardiac arrhythmias, each contain a stereogenic center bearing a secondary alcohol group. Reversed-phase achiral-chiral column-switching HPLC separations of the enantiomers of each compound were developed and validated for quantitation in plasma and other biofluids. The key component of the method was derivatization with 1-naphthyl isocyanate, which enhanced the sensitivity of fluorescence detection and enabled the enantiomers to be separated on a Pirkle column (covalent 3,5-dinitrobenzoyl-D-phenylglycine stationary phase). The lower limit of quantitation of ibutilide fumarate was typically 0.1 ng/ml or less of each enantiomer in 1 ml of plasma. Two of the special features of the column-switching system included operation with two samples in the system at one time, which reduced analysis time to 16 min/sample for ibutilide and 19 min/sample for artilide, and a relay-operated switching of detector outputs, which allowed achiral and chiral column chromatographic data to be gathered from two detectors into a single data acquisition channel.

Yeast cells lacking 5'-->3' exoribonuclease 1 contain mRNA species that are poly(A) deficient and partially lack the 5' cap structure

Analysis of the slowed turnover rates of several specific mRNA species and the higher cellular levels of some of these mRNAs in Saccharomyces cerevisiae lacking 5'-->3' exoribonuclease 1 (xrn1 cells) has led to the finding that these yeast contain higher amounts of essentially full-length mRNAs that do not bind to oligo(dT)-cellulose. On the other hand, the length of mRNA poly(A) chains found after pulse-labeling of cells lacking the exoribonuclease, the cellular rate of synthesis of oligo(dT)-bound mRNA, and the initial rate of its deadenylation appeared quite similar to the same measurements in wild-type yeast cells. Examination of the 5' cap structure status of the poly(A)-deficient mRNAs by comparative analysis of the m7G content of poly(A)- and poly(A)+ RNA fractions of wild-type and xrn1 cells suggested that the xrn1 poly(A)- mRNA fraction is low in cap structure content. Further analysis of the 5' termini by measurements of the rate of 5'-->3' exoribonuclease 1 hydrolysis of specific full-length mRNA species showed that approximately 50% of the xrn1 poly(A)-deficient mRNA species lack the cap structure. Primer extension analysis of the 5' terminus of ribosomal protein 51A (RP51A) mRNA showed that about 30% of the poly(A)-deficient molecules of the xrn1 cells are slightly shorter at the 5' end. The finding of some accumulation of poly(A)-deficient mRNA species partially lacking the cap structure together with the reduction of the rate of mRNA turnover in cells lacking the enzyme suggest a possible role for 5'-->3' exoribonuclease 1 in the mRNA turnover process.

Characterization of the XRN1 gene encoding a 5'-->3' exoribonuclease: sequence data and analysis of disparate protein and mRNA levels of gene-disrupted yeast cells

Sequencing of the XRN1 gene of Saccharomyces cerevisiae, cloned in this laboratory as a gene encoding a 160-kDa 5'-->3' exoribonuclease (XRN1), shows that it is identical to a gene (DST2 or SEP1) encoding a DNA strand transferase and to genes involved in nuclear fusion, KEM1, and plasmid stability, RAR5. To better understand the various phenotypes associated with loss of XRN1 and the enzymatic activities associated with the protein, certain characteristics of our yeast cells lacking an active gene (xrn1) have been examined. Cells are larger (average volume is x 1.5-1.8) and have an increased doubling time (x1.9-2.1). The protein synthesis rate per cell is 80-90% that of wild-type (wt) cells, and the resultant cellular protein levels are higher. The rate of the 25S and 18S rRNA synthesis is approximately 45% that of wt cells and its cellular level is about 90% that of wt cells. Levels of protein bands resolved by one-dimensional PAGE show substantial differences. Synthesis rates observed for the same protein bands, as well as measurements of several specific mRNA levels by Northern analysis, suggest disparities in mRNA levels. Results show two to four times longer half-lives of specific short-lived mRNAs. The variations in levels of protein and RNA species found in the xrn1 cells may be the cause of some of the phenotypes found associated with gene loss.

Fragments of the internal transcribed spacer 1 of pre-rRNA accumulate in Saccharomyces cerevisiae lacking 5'----3' exoribonuclease 1

The portion of the internal transcribed spacer 1 found on 20S pre-rRNA accumulates in Saccharomyces cerevisiae lacking 5'----3' exoribonuclease 1, showing that an endonucleolytic cleavage at the 3' terminus of 18S rRNA is involved in the 20S pre-rRNA to 18S mature rRNA conversion. Smaller fragments of the spacer sequence are also found. The exoribonuclease may be involved as a cytoplasmic RNase in the hydrolysis of the spacer.