Extracellular vesicles purified from serum-converted human platelet lysates offer strong protection after cardiac ischaemia/reperfusion injury

Extracellular vesicles (EVs) from cultured cells or bodily fluids have been demonstrated to show therapeutic value following myocardial infarction. However, challenges in donor variation, EV generation and isolation methods, and material availability have hindered their therapeutic use. Here, we show that human clinical-grade platelet concentrates from a blood establishment can be used to rapidly generate high concentrations of high purity EVs from sero-converted platelet lysate (SCPL-EVs) with minimal processing, using size-exclusion chromatography. Processing removed serum carrier proteins, coagulation factors and complement proteins from the original platelet lysate and the resultant SCPL-EVs carried a range of trophic factors and multiple recognised cardioprotective miRNAs. As such, SCPL-EVs protected rodent and human cardiomyocytes from hypoxia/re-oxygenation injury and stimulated angiogenesis of human cardiac microvessel endothelial cells. In a mouse model of myocardial infarction with reperfusion, SCPL-EV delivery using echo-guided intracavitary percutaneous injection produced large improvements in cardiac function, reduced scar formation and promoted angiogenesis. Since platelet-based biomaterials are already widely used clinically, we believe that this therapy could be rapidly suitable for a human clinical trial.

Modal analysis and efficient coupling of TE₀₁ mode in small-core THz Bragg fibers

We report a design of low-loss THz Bragg fibers with a core size on the order of wavelength that operates near the cutoff frequency of its TE01 mode. We also propose a broadband Y-type mode converter based on branched rectangular metallic waveguides to facilitate coupling between the TE01 mode of the Bragg fiber and the TEM mode in free space with 60% efficiency. Our fiber holds strong promise to facilitate beam-wave interaction in gyrotron for high-efficiency THz generation.

Accelerating effects of nonviable Staphylococcus aureus, its cell wall, and cell wall peptidoglycan

We have previously reported that local application of viable Staphylococcus aureus dramatically accelerates wound healing, but viable Staphylococcus epidermidis does not. Because the S. aureus effect occurred in the absence of infection and because the cell walls of the two bacterial species differ, we hypothesized that nonviable S. aureus, its cell wall, and its cell wall component(s) would accelerate healing. Nonviable S. aureus was prepared by chemical and physical means, and its cell wall and peptidoglycan was prepared from heat-killed cultures. In a large number of experiments, nonviable S. aureus (independent of the strain's protein A content), its cell wall, and peptidoglycan when instilled locally at the time of wounding each significantly increased the breaking strength of rat skin incisions (tested both in the fresh state and after formalin fixation). These agents also enhanced subcutaneous polyvinyl alcohol sponge reparative tissue collagen accumulation, generally by a factor of two. Histologic features of treated and control incisions were similar. In contrast, the reparative tissue of treated sponges contained more neutrophils, macrophages, capillaries, and collagen. These experimental data thus confirm our previous studies, as well as our hypothesis, and extend these observations of enhanced wound healing to specific fractions of the bacterial cell wall.

Molecular mechanisms underlying wound healing acceleration by Staphylococcus aureus peptidoglycan

Molecular mechanisms involved in wound healing acceleration by Staphylococcus aureus peptidoglycan were investigated with the use of polyvinyl alcohol sponges implanted under the dorsal skin of rats. Total collagen and RNA content and messenger RNA levels of alpha1(I) and alpha1(III) procollagen, transforming growth factor-beta1, and matrix metalloproteinase-1 were analyzed in saline solution- and S. aureus peptidoglycan-inoculated sponges at 4, 7, 14, and 21 days after implantation. S. aureus peptidoglycan-inoculated sponges on the fourth and seventh post-operative day were surrounded and penetrated by a thick capsule of reparative connective tissue. They were considerably heavier and contained more collagen and total RNA than saline solution-inoculated sponges. Histologically, the S. aureus peptidoglycan-inoculated sponges early on contained a denser infiltrate of polymorphonuclear cells than saline solution-inoculated sponges, and later fibroblasts, macrophages, collagen, and newly formed blood vessels were more abundant in the S. aureus peptidoglycan sponges. Matrix metalloproteinase-1 messenger RNA expression was elevated at 4 days in both sponge types. However, although matrix metalloproteinase-1 mRNA levels decreased to undetectable levels by 14 days in saline solution-inoculated sponges, they remained elevated throughout the 21-day study period in S. aureus peptidoglycan-inoculated sponges. No other significant differences in the parameters analyzed were detected. These results suggest that S. aureus peptidoglycan induces an accelerated but normal wound healing process in which the markedly increased early deposition of connective tissue is rapidly remodeled likely because of a sustained expression of matrix metalloproteinase-1.

Efficient heating with a controlled microwave field

To uncover the intriguing non-thermal microwave effect, an experiment was conducted using an amplifier rather than an oscillator as the radiation source, which was injected into an applicator with strong electromagnetic field enhancement. The characteristics of the applicator are discussed and the enhancement of the microwave field is illustrated and explained. Thermal distribution is simulated based on the calculated microwave field profile. It was demonstrated that the proposed system heated a SiC susceptor to a temperature of 637 °C with the input power of 60 W. The reasons for such an efficient heating are discussed.

X-ray microfabrication and measurement of a terahertz mode converter

Mode converters are critical for frequency-tunable terahertz gyrotrons. This study reports the development of a broadband TE(02) mode converter centered at 0.2 THz. An octafeed sidewall coupling structure was employed and the mode purity was analyzed. The converter was built using the technique of x-ray microfabrication. The x rays irradiated on the SU-8 resist and generated a template of very high thickness of 1.295 mm. Pulse electroplating technique was used to deposit copper on the structure along the template. The parts then went through precise machining and the residual resist was removed via high-flux radical etching. A computer-aided diagnostic system was introduced to measure the performance of the converter. Results suggest that the frequency response of resistivity should be taken into consideration for the devices in terahertz region.

Comparison of photodegradative efficiencies and mechanisms of Victoria Blue R assisted by Nafion-coated and fluorinated TiO2 photocatalysts

The purposes of this research were to study the effects of two modified photocatalysts, Nafion-coated TiO(2) and fluorinated TiO(2), and photocatalytic degradation of Victoria Blue R in aqueous solution. Photocatalytic degradation of Victoria Blue R was accelerated by the modified photocatalysts. Bulk and surface characterizations of the resulting powders were carried out. Attachment of the anions to the TiO(2) surface using the Nafion-coated-TiO(2) possibly results in increased adsorption of the cationic dye, and the degradation rate is larger for the cationic dye. It was found that Victoria Blue R on the two illuminated TiO(2) surfaces underwent very different changes. To obtain a better understanding on the mechanistic details of this modified-TiO(2)-assisted photodegradation of the Victoria Blue R dye with UV irradiation, a large number of intermediates of the process were separated, identified, and characterized by a high-performance liquid chromatography-mass spectrometry technique. Several probable photodegradation pathways were proposed and discussed.

Measurement of angular distributions of Drell-Yan dimuons in p+p interactions at 800 GeV/c

We report a measurement of the angular distributions of Drell-Yan dimuons produced using an 800 GeV/c proton beam on a hydrogen target. The polar and azimuthal angular distribution parameters have been extracted over the kinematic range 4.5<m micromicro<15 GeV/c2 (excluding the Upsilon resonance region), 0<p T <4 GeV/c, and 0<x F<0.8. The p+p angular distributions are similar to those of p+d, and both data sets are compared with models which attribute the cos2varphi distribution either to the presence of the transverse-momentum-dependent Boer-Mulders structure function h1 perpendicular to 1 or to QCD effects. The data indicate the need to include QCD effects before reliable information on the Boer-Mulders function can be extracted. The validity of the Lam-Tung relation in p+p Drell-Yan data is also tested.

High-power millimeter-wave rotary joint

The rotary joint is a useful microwave component that connects a fixed part to a rotatable part. This study systematically analyzes the effect of the discontinuity on the interface of a rotary joint for several waveguide modes. Simulation results indicate that the transmission of the TE(01) mode is independent of the geometry of the joint, and thus is ideal for such application. A rotary joint consisting of two identical TE(01) mode converters, clasped each other by a bearing, is designed, fabricated, and tested. Back-to-back transmission measurements exhibit an excellent agreement to the results of computer simulations. The measured optimum transmission is 97% with a 3 dB bandwidth of 8.5 GHz, centered at 35.0 GHz. The cold measurement shows that the results are independent of the angle of rotation. In addition, a high-power experiment is conducted. The just developed rotary joint can operate up to a peak input power of 210 W with a duty of 18%. The working principle, although demonstrated in the millimeter-wave region, can be applied up to the terahertz region where the joint gap is generally critical except for the operating TE(01) mode.

Measurement of Upsilon production for p + p and p + d interactions at 800 GeV/c

We report a high statistics measurement of Upsilon production with an 800 GeV/c proton beam on hydrogen and deuterium targets. The dominance of the gluon-gluon fusion process for Upsilon production at this energy implies that the cross section ratio, sigma(p+d-->Upsilon)/2sigma(p+p-->Upsilon), is sensitive to the gluon content in the neutron relative to that in the proton. Over the kinematic region 0<x(F)<0.6, this ratio is found to be consistent with unity, in striking contrast to the behavior of the Drell-Yan cross section ratio sigma(p+d)(DY)/2sigma(p+p)(DY). This result shows that the gluon distributions in the proton and neutron are very similar. The Upsilon production cross sections are also compared with the p+d and p+Cu cross sections from earlier measurements.

Effect of microwave annealing temperatures on lead zirconate titanate thin films

Lead zirconate titanate (Pb(1.1)(Zr(0.52)Ti(0.48))O(3)) thin films of thickness 260 nm on Pt/Ti/SiO(2)/Si substrates were densified by 2.45 GHz microwave annealing. The PZT thin films were annealed at various annealing temperatures from 400 to 700 °C for 30 min. X-ray diffraction showed that the pyrochlore phase was transformed to the perovskite phase at 450 °C and the film was fully crystallized. The secondary (again pyrochlore) phase was observed in the PZT thin films, which were annealed above 550 °C. The surface morphologies were changed above 550 °C of the PZT thin films due to the secondary phase. Higher dielectric constant (ε(r)) and lower dielectric loss coercive field (E(c)) were achieved for the 450 °C film than for the other annealed films.

Measurement of angular distributions of Drell-Yan dimuons in p+d interactions at 800 GeV/c

We report a measurement of the angular distributions of Drell-Yan dimuons produced using an 800 GeV/c proton beam on a deuterium target. The muon angular distributions in the dilepton rest frame have been measured over the kinematic range 4.5<m{mu mu}<15 GeV/c{2}, 0<p{T}<4 GeV/c, and 0<x{F}<0.8. No significant cos2phi dependence is found in these proton-induced Drell-Yan data, in contrast with the situation for pion-induced Drell-Yan data. The data are compared with expectations from models which attribute the cos2phi distribution to a QCD vacuum effect or to the presence of the transverse-momentum-dependent Boer-Mulders structure function h{1}{perpendicular}. Constraints on the magnitude of the sea-quark h{1}{perpendicular} structure functions are obtained.

Staphylococcus aureus peptidoglycan ameliorates cyclophosphamide-induced impairment of wound healing

Cyclophosphamide given systemically to rats leads to impaired wound healing, characterized by decreases in the inflammatory reaction, fibroplasia, neovascularization, reparative collagen accumulation, and wound breaking strength. In contrast, the local application of Staphylococcus aureus peptidoglycan at the time of wounding increases all of these processes in normal rats. Accordingly, we hypothesized that inoculation of S. aureus peptidoglycan into wounds of cyclophosphamide-treated rats would ameliorate the otherwise impaired healing. Dorsal bilateral skin incisions and subcutaneous implantation of polyvinyl alcohol sponges (two on each side) were performed on male Sprague-Dawley rats receiving either saline or cyclophosphamide (24 mg/kg) intraperitoneally at the time of operation, on postoperative days 1, 2, 3, 4 (for rats killed on postoperative day 7), and also on day 8 (for rats killed on postoperative day 14). The incisions on one side were inoculated at the time of closure with 0.2 ml of saline solution, and the incisions on the other side with 6 mg S. aureus peptidoglycan in 0.2 ml saline solution (860 microg/cm incision). The sponges were instilled with 0.1 ml saline solution on the saline solution-instilled incision side or with S. aureus peptidoglycan 0.5 mg/sponge) in 0.1 ml saline solution on the other side. In control rats receiving saline solution intraperitoneally, incisions treated with S. aureus peptidoglycan were significantly stronger than saline solution-treated incisions by a factor of 1.8 at 1 week (p < 0.001); at 2 weeks the increase was small and not significant. Cardiac blood leukocytes and platelets fell markedly (90%) in cyclophosphamide- treated rats, and there was a decrease in wound breaking strength of their saline-treated incisions at both 7 and 14 days compared with saline solution-treated incisions of control rats. S. aureus peptidoglycan treatment of the wounds completely prevented this effect at 7 days, and partially at 14 days. Polyvinyl alcohol sponge reparative tissue hydroxyproline, 7 days after surgery, was decreased in cyclophosphamide-treated rats; this was completely prevented by S. aureus peptidoglycan treatment of the sponges. Histologically, the inflammatory response to the wounding, influx of macrophages and fibroblasts, angiogenesis, and collagen accumulation were all reduced at day 7 and 14 after surgery in the sponge reparative tissue of cyclophosphamide- treated rats; this was prevented by S. aureus peptidoglycan treatment of the sponges. In conclusion, a single local application of S. aureus peptidoglycan ameliorates cyclophosphamide-impaired wound healing.

Single local instillation of nonviable Staphylococcus aureus or its peptidoglycan ameliorates glucocorticoid-induced impaired wound healing

An excess in glucocorticoid steroids, either from endogenous or exogenous sources, has been shown to inhibit wound repair. Key to this impairment is a diminution of the inflammatory response to wounding, fibroplasia, capillary formation, reparative tissue collagen accumulation, and wound breaking strength. Because a single local application at operation of nonviable Staphylococcus aureus or its peptidoglycan increases all of these processes in normal rats, we hypothesized that nonviable S. aureus and S. aureus peptidoglycan would each ameliorate glucocorticoid-induced impaired healing. Sprague-Dawley male rats aseptically received two 7 cm paravertebral skin incisions and underwent subcutaneous implantation of polyvinyl alcohol sponges. Two glucocorticoids were used: hydrocortisone, 8 mg intramuscularly, daily beginning 1 day before operation and continuing during the postoperative period; or a single dose of a long-acting preparation of methylprednisolone, 6 or 8 mg intramuscularly, on the day before operation. Controls received intramuscular injections of saline solution at the same respective times. At the time of the operation, one incision and the polyvinyl alcohol sponges on one side of the animal were instilled with saline solution while the incision and sponges on the opposite side were instilled with nonviable S. aureus (hydrocortisone study) or S. aureus peptidoglycan (two methylprednisolone studies). The data showed that, at postoperative day 7, the single local application at wounding of nonviable S. aureus or S. aureus peptidoglycan increased wound breaking strength in the control rats by factors of 1.6 in the hydrocortisone experiment and 1.4 and 1.6 in the methylprednisolone studies. These treatments prevented (in hydrocortisone-treated rats) or mitigated (in methylprednisolone-treated rats) the glucocorticoid-induced decrease in wound breaking strength. In addition, these treatments prevented the glucocorticoid-induced decreases in the inflammatory (largely mononuclear cells) response to wounding and in the accumulation within the polyvinyl alcohol sponge of reparative tissue fibroblasts, capillaries, and collagen.

Variation in Bentgrass Susceptibility to Typhula incarnata and in Isolate Aggressiveness Under Controlled Environment Conditions

Typhula incarnata, the causal agent of gray snow mold, is an important winter pathogen of turfgrasses in the northern United States. The relative susceptibility of cultivars of three bent-grass species (creeping, colonial, and velvet bentgrass) to Typhula incarnata and the aggressiveness of 15 T. incarnata isolates obtained from infected turfgrasses on golf courses in Michigan, Minnesota, and Wisconsin were evaluated under controlled conditions. A hypersensitive type of resistance response to T. incarnata was not observed in any cultivar. Disease severity increased with higher inoculum concentration of T. incarnata. Colonization by gray snow mold gradually decreased with increasing plant age from 11 weeks after seeding in most cultivars tested, suggesting that age-related resistance was expressed over time. There were significant differences in disease severity among the three bentgrass species, particularly between tetraploid (creeping and colonial) and diploid (velvet) species, and among cultivars within each species, indicating varying levels of susceptibility to T. incarnata. All 15 isolates were pathogenic on bentgrass and were significantly different in aggressiveness, but aggressiveness was not related to geographic origin. Therefore, turfgrass breeders should be able to use one or a few virulent representative isolates of the pathogen to screen for resistance.

Rise and fall time behavior of the gyrotron backward-wave oscillator

The rise and fall time behavior of a pulsed microwave oscillator is a problem of academic interest. It is also of importance to radar and other applications because it can lead to phase and frequency jitters or even lock the entire pulse into an undesired mode. Here we present a study of the rise and fall time behavior in the gyrotron backward-wave oscillator (gyro-BWO). Single-mode simulations reveal that, during the rise and fall portions of the electron beam pulse, oscillation frequencies of the axial modes vary in such a way that their transit angles remain at the respective optimum values. Thus, axial mode competition and mode switching can readily take place in these transient stages. Time-dependent simulations demonstrate that, under both the gradual and instant turn-on conditions, the axial modes compete in a pattern governed by the characteristic asymmetry of the mode profiles. Other aspects of physics interest include the analysis and explanation of a resultant hysteresis effect between the rise and fall portions of the beam pulse. These understandings are expected to provide the basis for achieving a stable gyro-BWO operating at a single mode throughout the entire beam pulse.

Transition of absolute instability from global to local modes in a gyrotron traveling-wave amplifier

The gyrotron traveling-wave amplifier employing the distributed-loss scheme is capable of very high gain and effective in suppressing the global absolute instabilities. This study systematically characterizes the local absolute instabilities and their transitional behavior. The local absolute instabilities are analyzed using a model that incorporates the penetration of the field from the copper section into the lossy section. The axial modes were characterized from the perspective of beam-wave interaction and were found to share many characteristics with the global modes. The transition from global modes to local modes as the distributed loss increases was demonstrated. The electron transit angle in the copper section, which determines the feedback criterion, governs the survivability of an oscillation. In addition, the oscillation thresholds predicted using this model are more accurate than those obtained using a simplified model.

Aggressiveness of Typhula ishikariensis Isolates to Cultivars of Bentgrass Species (Agrostis spp.) Under Controlled Environment Conditions

Speckled snow mold, caused by Typhula ishikariensis, is one of the most important Typhula snow molds in subarctic zones of the Northern Hemisphere. Nine isolates of three T. ishikariensis varieties (var. ishikariensis, var. canadensis, and var. idahoensis) isolated from infected turfgrasses on golf course fairways throughout Wisconsin were evaluated for their aggressiveness toward nine cultivars of three bentgrass species (three creeping, three colonial, and three velvet cultivars) under controlled environmental conditions. Speckled snow mold severity increased as inoculum concentration of T. ishikariensis was increased. In general, bentgrass susceptibility increased between 9 and 11 weeks after seeding but gradually decreased thereafter, suggesting expression of age-related resistance as plants matured. Significant differences in aggressiveness were detected within and among T. ishikariensis varieties. Significant interactions between T. ishikariensis varieties or isolates and bentgrass species were detected, but there was no interaction between pathogen isolates and bentgrass cultivars. Disease severity evaluations showed significant differences among bentgrass cultivars and species in their response to T. ishikariensis. Since bentgrass species exhibit differential responses to T. ishikariensis varieties, representative isolates of each variety should be employed for screening of bentgrass germplasm for resistance to speckled snow mold.

Dynamics of mode competition in the gyrotron backward-wave oscillator

The axial modes of the gyrotron backward-wave oscillator (gyro-BWO) each exhibit a distinctive asymmetry in axial field profile. As a result, and in sharp contrast to the behavior of the familiar resonator-based gyrotron oscillator, particle simulations of the gyro-BWO reveal a radically different pattern of mode competition in which a fast-growing and well-established mode is subsequently suppressed by a later-starting mode with a more favorable field profile. This is verified in a Ka-band experiment and the interaction dynamics are elucidated with a time-frequency analysis.

Absolute instabilities in a high-order-mode gyrotron traveling-wave amplifier

The absolute instability is a subject of considerable physics interest as well as a major source of self-oscillations in the gyrotron traveling-wave amplifier (gyro-TWT). We present a theoretical study of the absolute instabilities in a TE01 mode, fundamental cyclotron harmonic gyro-TWT with distributed wall losses. In this high-order-mode circuit, absolute instabilities arise in a variety of ways, including overdrive of the operating mode, fundamental cyclotron harmonic interactions with lower-order modes, and second cyclotron harmonic interaction with a higher-order mode. The distributed losses, on the other hand, provide an effective means for their stabilization. The combined configuration thus allows a rich display of absolute instability behavior together with the demonstration of its control. We begin with a study of the field profiles of absolute instabilities, which exhibit a range of characteristics depending in large measure upon the sign and magnitude of the synchronous value of the propagation constant. These profiles in turn explain the sensitivity of oscillation thresholds to the beam and circuit parameters. A general recipe for oscillation stabilization has resulted from these studies and its significance to the current TE01 -mode, 94-GHz gyro-TWT experiment at UC Davis is discussed.

J/psi polarization in 800-GeV p-Cu interactions

We present measurements of the polarization of the J/psi produced in 800-GeV proton interactions with a copper target. Polarization of the J/psi is sensitive to the ccmacr; production and hadronization processes. A longitudinal polarization is observed at large x(F), while at small x(F) the state is produced essentially unpolarized or slightly transversely polarized. No significant variation of the polarization is observed versus p(T).

Linear and time-dependent behavior of the gyrotron backward-wave oscillator

Formation of axial modes in the gyrotron backward-wave oscillator is examined in the perspective of optimum conditions for beam-wave interactions. Distinctive linear properties are revealed and interpreted physically. Nonlinear implications of these properties (specifically, the role of high-order axial modes) are investigated with time-dependent simulations. Nonstationary oscillations exhibit self-modulation behavior while displaying no evidence of axial mode competition. Reasons for the erratic frequency tuning are investigated and stable tuning regimes are identified as a remedy.

Visualization of new virus-like-particles in Trichomonas vaginalis

In the present work, we demonstrate virus-like particles (VLPs) with various morphological variations in Trichomonas vaginalis. The VLPs were distinct based on size, shape and electron density, with VLPs being either electron-dense or electron-lucent. We used electron microscopy thin sections of several T. vaginalis strains virus-infected, and also negative staining of fractions obtained after purification by CsCl buoyant density gradient centrifugation. The particles observed in fractions are identical to those previously described, but by thin sections, we found new forms. The shapes found were icosahedral, spherical and oblong, and the sizes varied from 33 to 120nm in diameter with the most common VLP being spherical and having a size range from 83 to 104nm. The VLPs were found in the cytoplasm closely associated with the Golgi complex, with some VLPs budding from the Golgi, and other VLPs were detected adjacent to the plasma membrane. Unidentified cytoplasmic inclusions were observed in the region close to the VLPs and Golgi. Clusters of the already described icosahedral virus were also observed in the cytoplasm, although less frequently. These results indicate that T. vaginalis organisms may be infected with different dsRNA viruses simultaneously.

Characterization of stationary and nonstationary behavior in gyrotron oscillators

The transition from the stationary state to a sequence of nonstationary states in the gyromonotron oscillator is experimentally characterized for the first time. We have also demonstrated the stationary operation of a gyrotron backward-wave oscillator at a beam current far in excess of the generally predicted nonstationary threshold. This difference in nonlinear behavior has been investigated and shown to be fundamental with a comparative analysis of the feedback mechanisms, energy deposition profiles, and field shaping processes involved in these two types of oscillations.

Primary tumour volume delineation in nasopharyngeal carcinoma and correlation with 1997 AJCC tumour stage classification

OBJECTIVE

To investigate the variability in primary tumour volume in nasopharyngeal carcinoma and compare it with the tumour staging of the 1997 American Joint Committee on Cancer.

DESIGN

Prospective study.

SETTING

Tertiary care centre.

METHOD

A series of 33 newly diagnosed patients who were treated with high-dose radiotherapy participated in the study.

MAIN OUTCOME MEASURES

Using computed tomographic scans, primary tumour volumes were measured using the summation-of-areas technique, and the variability in tumour volume was determined. The Mann-Whitney test was used for statistical analysis.

RESULTS

A large variation in primary tumour volume was observed, especially in advanced-stage cases.

CONCLUSIONS

Nasopharyngeal carcinoma shows considerable variability in primary tumour volume. Incorporation of primary tumour volume may lead to further refinement of the 1997 tumour staging system.

Does a reduction in family medicine clerkship time affect educational outcomes?

BACKGROUND AND OBJECTIVES

Little is known about the relationship between the length of a family medicine clerkship and its educational outcomes. After our family medicine clerkship time decreased from 6 weeks to 4 weeks in July 1997, we studied how this change in clerkship length affected educational outcomes.

METHODS

Educational outcomes for the 2-year periods before and after the change were examined and compared whenever possible. Outcome measurements included student ratings of different aspects of the clerkship and student performance on clerkship examinations.

RESULTS

Students' exposure to common clinical problems was unaffected by the change. For the 4-week clerkship, there was a slight increase in student ratings of the adequacy of number of patients seen, the opportunity to follow-up with patients, the ability to develop health promotion plans, and overall satisfaction. Because the combinations of examinations used differed each year, student performance on clerkship examinations could not be directly compared.

CONCLUSIONS

Educational outcomes of the 4-week clerkship were similar to the 6-week clerkship. A few key outcomes improved. Various curricular and structural changes instituted for the 4-week clerkship contributed to the stability in outcomes. Reports from other medical schools may give additional insight into understanding this relationship.

Observation of polarization in bottomonium production at square root of s = 38.8 GeV

We present a measurement of the polarization observed for bottomonium states produced in p-Cu collisions at square root of s = 38.8 GeV. The angular distribution of the decay dimuons of the Upsilon(1S) state shows no polarization at small values of the fractional longitudinal momentum x(F) and transverse momentum p(T) but significant positive transverse production polarization for either p(T)>1.8 GeV/c or for x(F)>0.35. The Upsilon(2S+3S) (unresolved) states show a large transverse production polarization at all values of x(F) and p(T) measured. These observations challenge NRQCD calculations of the polarization expected in the hadronic production of bottomonium states.

Specific alterations of U1-C protein or U1 small nuclear RNA can eliminate the requirement of Prp28p, an essential DEAD box splicing factor

While some members of the ubiquitous DExD/H box family of proteins have RNA helicase activity in vitro, their roles in vivo remain virtually unknown. Here, we show that the function of an otherwise essential DEAD box protein, Prp28p, can be bypassed by mutations that alter either the protein U1-C or the U1 small nuclear RNA. Further analysis suggests that the conserved L13 residue in the U1-C protein makes specific contact to stabilize the U1 snRNA/5' splice site duplex in the prespliceosome, and that Prp28p functions to counteract the stabilizing effect of the U1-C protein, thereby promoting the dissociation of the U1 small nuclear ribonucleoprotein particle from the 5' splice site. Thus, in addition to unwinding RNA, the DExD/H box proteins may affect RNA-RNA rearrangements by antagonizing specific RNA-stabilizing proteins.

Modular long-range regulation of Myf5 reveals unexpected heterogeneity between skeletal muscles in the mouse embryo

The myogenic factor Myf5 plays a key role in muscle cell determination, in response to signalling cascades that lead to the specification of muscle progenitor cells. We have adopted a YAC transgenic approach to identify regulatory sequences that direct the complex spatiotemporal expression of this gene during myogenesis in the mouse embryo. Important regulatory regions with distinct properties are distributed over 96 kb upstream of the Myf5 gene. The proximal 23 kb region directs early expression in the branchial arches, epaxial dermomyotome and in a central part of the myotome, the epaxial intercalated domain. Robust expression at most sites in the embryo where skeletal muscle forms depends on an enhancer-like sequence located between −58 and −48 kb from the Myf5 gene. This element is active in the epaxial and hypaxial myotome, in limb muscles, in the hypoglossal chord and also at the sites of Myf5 transcription in prosomeres p1 and p4 of the brain. However later expression of Myf5 depends on a more distal region between −96 and −63 kb, which does not behave as an enhancer. This element is necessary for expression in head muscles but strikingly only plays a role in a subset of trunk muscles, notably the hypaxially derived ventral body muscles and also those of the diaphragm and tongue. Transgene expression in limb muscle masses is not affected by removal of the −96/-63 region. Epaxially derived muscles and some hypaxial muscles, such as the intercostals and those of the limb girdles, are also unaffected. This region therefore reveals unexpected heterogeneity between muscle masses, which may be related to different facets of myogenesis at these sites. Such regulatory heterogeneity may underlie the observed restriction of myopathies to particular muscle subgroups.

Saturated behavior of the gyrotron backward-wave oscillator

Physical processes in the gyrotron backward-wave oscillator (gyro-BWO) are investigated theoretically. Results indicate highly current-sensitive field profiles and hence sharply contrasting linear and saturated behaviors. The linear field extends over the entire structure length, whereas the saturated profile depends strongly on the energetics in the internal feedback loop. It is shown that this distinctive feature substantially influences the basic properties of the gyro-BWO including the start-oscillation current, efficiency, power scaling, and stability of tuning.

Wound healing: captopril, an angiogenesis inhibitor, and Staphylococcus aureus peptidoglycan

BACKGROUND

Captopril, an angiotensin-converting enzyme inhibitor, used for treating hypertension and heart failure, inhibits angiogenesis in the corneas of rats in response to basic fibroblast growth factor, slows the growth of experimental tumors in rats, and leads to the regression of Kaposi's sarcoma. Because angiogenesis is key to wound healing, we hypothesized that captopril would impair wound healing. We hypothesized also that because local application at operation of Staphylococcus aureus peptidoglycan (SaPG) increases angiogenesis and accelerates wound healing in rats, SaPG would prevent or ameliorate the postulated captopril-impaired wound healing.

MATERIALS AND METHODS

In each experiment, rats were divided randomly into two groups: one drinking tap water, and the other, tap water containing 0.5 mg captopril/ml. All ate chow and drank ad libitum, pre-operatively (4-12 days) and postoperatively (7 days). In experiments 1 and 2, bilateral paravertebral 5.5-cm skin incisions were made aseptically (intraperitoneal sodium pentobarbital), and closed with interrupted No. 35 stainless-steel sutures. On one side, the wound was immediately inoculated with 157 microliter pyrogen-free isotonic saline and on the other side the wound was inoculated with 157 microliter saline containing 4.7 mg SaPG (860 microgram SaPG/cm incision). In the third experiment, polyvinyl alcohol (PVA) sponges (16-17 mg dry wt each) containing either 50 microliter saline or 0.5 mg SaPG in 50 microliter saline were implanted subcutaneously, two on each side, via 1-cm incisions closed with a single suture. In the fourth experiment, 5.5-cm bilateral skin incisions and subcutaneous implantation of PVA sponges were done as described but all sites were instilled with saline only. All rats were euthanized (CO(2) asphyxia) 7 days postoperatively.

RESULTS

Wound breaking strength (WBS) of the saline-treated incisions was significantly higher (P < 0.001) in captopril-treated rats than in controls (172 +/- 13 g vs 105 +/- 6 g) in experiment 1 and higher, but not significantly in captopril-treated rats in experiment 2 (153 +/- 8 g vs 114 +/- 6 g) (PNS). SaPG inoculation of the incisions increased WBS significantly in both control and captopril-treated rats: 187 +/- 11 g vs 105 +/- 6 g (P < 0.001) and 283 +/- 16 g vs 172 +/- 13 g (P < 0.001), respectively, in experiment 1, and 217 +/- 13 g vs 114 +/- 6 g (P < 0.0001) (controls) and 266 +/- 17 g vs 153 +/- 8 g (captopril-treated rats) (P < 0.0001) in experiment 2. In experiment 3, subcutaneous PVA saline-inoculated sponge reparative tissue hydroxyproline (OHP) content was similar in control and captopril-treated rats, and SaPG inoculation increased reparative tissue OHP significantly in both groups: 2458 +/- 218 microgram/100 mg dry sponge vs 3869 +/- 230 microgram/100 mg (P < 0.001) (controls) and 2489 +/- 166 microgram/100 mg vs 4176 +/- 418 microgram/100 mg (P < 0.001) (captopril-treated rats). Histologically, angiogenesis and reparative tissue collagen were similar in control and captopril-treated rats, in both saline-inoculated and SaPG-inoculated sponges. In experiment 4 (all incisions and subcutaneous PVA sponges were saline-inoculated), there was no significant difference in WBS between control and captopril-treated rats (107 +/- 6 g vs 96 +/- 5 g, NS). PVA sponge reparative tissue OHP was significantly higher in captopril-treated rats: 3698 +/- 170 microgram/100 mg dry sponge vs 2534 +/- 100 microgram/100 mg (P < 0.0001).

CONCLUSION

Unexpectedly, in four experiments, captopril did not inhibit WBS or PVA sponge reparative tissue angiogenesis or collagen accumulation; in fact, WBS was increased significantly in one of three experiments, and PVA sponge reparative tissue OHP was increased significantly in one of two experiments. Also, captopril did not interfere with the wound healing-accelerating effect of SaPG.

Gastroesophageal variceal bleeding caused by hepatoportal arteriovenous fistula

Hepatoportal arteriovenous fistulas are usually traumatic in origin and may result in portal hypertension and serious complications. We report a 34-year-old female with a history of abdominal trauma, who developed symptoms of tarry stools and hematemesis 5 years later. Esophageal and gastric varices with bleeding were diagnosed by upper gastrointestinal endoscopy. Abdominal ultrasonography and computerized tomography favored noncirrhotic portal hypertension. An extrahepatic hepatoportal arteriovenous fistula was demonstrated by angiography. The patient underwent surgery to correct the condition. The liver had a smooth surface and both the common hepatic and gastroduodenal arteries were ligated during surgery. The postoperative course was uneventful. The varices later disappeared.

Measurement of differences between J/psi and psi(') suppression in p-A collisions

Measurements of the suppression of the yield per nucleon of J/psi and psi(') production for 800 GeV/ c protons incident on heavy nuclear targets, relative to light nuclear targets, have been made with very broad coverage in x(F) and p(T). The observed suppression is smallest at x(F) values of 0.25 and below, and increases at larger values of x(F). It is also strongest at small p(T). Substantial differences between psi(') and J/psi production are observed for the first time in p-A collisions. The suppression for psi(') production is stronger than that for J/psi for x(F) near zero, but becomes comparable to that for J/psi for x(F)>0.6.

Induction of differentiation and apoptosis by ligands of peroxisome proliferator-activated receptor gamma in non-small cell lung cancer

The peroxisome proliferator-activated receptor gamma (PPARgamma) is a ligand-activated transcription factor belonging to the steroid receptor superfamily. It is a key regulator of adipogenic differentiation, the ligands of which have also been demonstrated to induce differentiation in human breast and colon cancer cell lines. This study examined PPARgamma, in non-small cell lung cancer (NSCLC). PPARgamma mRNA and protein were expressed in NSCLC cell lines, with highest levels in adenocarcinomas. PPARgamma protein was also expressed in 50% of primary lung cancers by immunohistochemistry. Treatment of multiple cell lines with two distinct PPARgamma ligands in the presence of serum resulted in growth arrest, irreversible loss of capacity for anchorage-independent growth, decreased activity and expression of matrix metalloproteinase 2, and modulation of multiple markers in a manner consistent with differentiation. Specifically, there was up-regulation of general markers of the differentiated state such as gelsolin, Mad, and p21. Down-regulation of specific markers of progenitor lineages for the peripheral lung, i.e., the type II pneumocyte lineage markers MUC1 and surfactant protein-A and the Clara cell lineage marker CC10, also occurred. In addition, HTI56, a marker of terminally differentiated type I pneumocytes, was also induced. Consistent with a more mature, less malignant phenotype, ligand treatment also inhibited the expression of cyclin D1 and led to hypophosphorylation of the retinoblastoma protein. In contrast, in the absence of serum, ligand treatment rapidly resulted in apoptosis and substantially earlier onset of differentiation. Taken together, these results show that depending on the growth milieu, ligands of PPARgamma induce differentiation and apoptosis in NSCLC, suggesting clinical utility for these agents.

Prediction of the rates of fertilization, cleavage, and pregnancy success by cumulus-coronal morphology in an in vitro fertilization program

OBJECTIVE

To examine the relation between the grading of cumulus-coronal morphology at oocyte retrieval and the rates of fertilization, cleavage, and pregnancy success in IVF-ET cycles.

DESIGN

Retrospective study.

SETTING

University-affiliated medical center.

PATIENT(S)

Infertile women who underwent IVF-ET treatment.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Fertilization and cleavage of the oocytes and the pregnancy outcome.

RESULT(S)

Mature grade 3 cumulus-oocyte complexes (COCs) constituted the highest percentage among all grades and had a higher fertilization rate than COCs of other grades (77% versus 65%, 43%, and 28% for grades 2, 1, and 4, respectively). The cleavage and polyspermy rates did not correlate with cumulus-coronal morphology grading. The pregnancy rate was higher in cycles with >50% grade 3 COCs than in cycles with < or =50% grade 3 COCs (32% versus 16%). In cycles with >80% grade 3 COCs, the pregnancy rate was 57%. The correlation between the percentage of grade 3 COCs and the pregnancy rate was independent of patient age and the number of COCs retrieved.

CONCLUSION(S)

The cumulus-coronal morphology grade correlates with the fertilization rate but not with the cleavage or polyspermy rate. In vitro fertilization cycles that have a greater percentage of grade 3 COCs have an increased chance of resulting in pregnancy. The cumulus-coronal morphology grade predicts pregnancy success in IVF-ET cycles.

Induction of differentiation accompanies inhibition of Cdk2 in a non-small cell lung cancer cell line

Induction of differentiation in a variety of model systems is accompanied by cell cycle exit and inhibition of Cdk2 kinase activity. We asked whether inhibition of Cdk2 activity is sufficient to allow differentiation to occur in a non-small cell lung cancer cell line. Treatment of NCI-H358 with flavopiridol, an inhibitor of multiple Cdk's, resulted in growth arrest and induction of mucinous differentiation. The onset of differentiation coincided temporally with loss of Cdk2 kinase activity. Western analysis revealed that flavopiridol treatment resulted in depletion of both cyclin E and D1, suggesting that loss of the regulatory subunits is at least partially responsible for the loss of Cdk kinase activity. Similarly, roscovitine, an inhibitor of Cdk's 1, 2, and 5, but not Cdk4, also induced differentiation in NCI-H358, although the resulting pattern of expression of cell cycle regulatory genes differed from the pattern obtained with flavopiridol. Furthermore, stable expression of an antisense Cdk2 construct in NCI-H358 also resulted in the appearance of a marker of mucinous differentiation. These results show that the inhibition of activity of cyclin dependent kinases, particularly Cdk2, by multiple different mechanisms is accompanied by differentiation. Thus, induction of differentiation is one potential mechanism of action for agents that down-regulate Cdk activity.

Single local instillation of Staphylococcus aureus peptidoglycan prevents diabetes-induced impaired wound healing

Diabetes-induced impaired wound healing is characterized by inhibition of the inflammatory response to wounding, macrophage infiltration, angiogenesis, fibroplasia, reparative collagen accumulation, and wound breaking strength. Because all of these processes are accelerated in normal rats by a single local application at operation of Staphylococcus aureus peptidoglycan, we hypothesized that S. aureus peptidoglycan would prevent diabetes-induced impaired wound healing, despite persistent, untreated hyperglycemia, polydipsia, glycosuria, and polyuria. Sprague- Dawley male rats were divided into two groups. One group received an intraperitoneal injection of streptozotocin (65 mg/kg) in citrate solution; the other group received an intraperitoneal injection of an equivalent volume of citrate solution. Seventeen days after the injections, the diabetic and control rats received aseptically two 5.5-cm paravertebral incisions and subcutaneous implantation of six polyvinyl alcohol sponges, three on each side. On one side, each sponge contained 0.5 mg S. aureus peptidoglycan in 50 microliter saline solution, and the incision was inoculated along its length with 4.7 mg S. aureus peptidoglycan in 157 microliter saline solution (860 microgram/S. aureus peptidoglycan/cm incision); on the other side, the same respective volumes of saline were used. During the preoperative and postoperative periods, diabetic rats lost a small amount of weight (2%), were hyperglycemic (363 +/- 10 mg/100 ml blood), polydipsic, glycosuric, and polyuric, whereas the controls gained weight (25%) and were normoglycemic (104 +/- 5 mg/100 ml blood); these differences were significantly different (p <.001 in each case). In controls, S. aureus peptidoglycan inoculation increased wound breaking strength (by a factor of 2.0) and hydroxyproline content (by a factor of 1.4; p <.001 in each case); in diabetics, there were significant decreases in wound breaking strength (by a factor of 1.7) and hydroxyproline content (by a factor of 1.3) of saline solution-inoculated incisions and sponges compared with the wound breaking strength and hydroxyproline content of saline solution-inoculated incisions and sponges in controls (p <.02 and p <.001, respectively). These decreases were completely prevented when the incisions and polyvinyl alcohol sponges had been inoculated at operation with S. aureus peptidoglycan; S. aureus peptidoglycan inoculation in the diabetic rats increased wound breaking strength by a factor of 2.2 and sponge reparative tissue hydroxyproline by a factor of 1.6 (p <.001 in each case). Thus, diabetes-induced impaired wound healing was prevented completely by a single local instillation at operation of S. aureus peptidoglycan, despite persistent, untreated hyperglycemia, polydipsia, polyuria, and glycosuria.

A novel GFPneo vector designed for the isolation and analysis of enhancer elements in transfected mammalian cells

We have designed a new approach to the direct cloning and rapid analysis of mammalian enhancer elements by fusing green fluorescent protein and neomycinphosphotransferase under the control of a thymidine kinase minimal promoter. DNA fragments containing known or potential enhancer elements can be inserted into a polylinker upstream of GFPneo and re-isolated from stably transfected cell lines by a direct transgene-specific polymerase chain reaction (PCR), for further analysis. C2C12 muscle cells were transfected with four vectors containing the GFPneo fusion gene regulated by the cytomegalovirus promoter, the myoD distal core enhancer and myoblast- and myotube-specific enhancers from the desmin gene. GFPneo shows robust epifluorescence by microscopy and flow cytometry and retains sufficient neo activity to permit selection of G418-resistant clones. The fluorescence signal pattern of GFPneo expressed under the control of the desmin enhancers mirrors their transcriptional profile during myogenic differentiation. This finding demonstrates the value of GFPneo as a tool to analyse differentiation stage-specific regulatory DNA elements in stably transfected mammalian cell lines. We were able to re-isolate the myoD enhancer mediating GFPneo expression from a stably transfected C2C12 clone by a transgene-specific PCR reaction, demonstrating the feasibility of using this new vector system for the isolation of regulatory sequences.

Dbp5p, a cytosolic RNA helicase, is required for poly(A)+ RNA export

The DBP5 gene encodes a putative RNA helicase of unknown function in the yeast Saccharomyces cerevisiae. It is shown here that Dbp5p is an ATP-dependent RNA helicase required for polyadenylated [poly(A)+] RNA export. Surprisingly, Dbp5p is present predominantly, if not exclusively, in the cytoplasm, and is highly enriched around the nuclear envelope. This observation raises the possibility that Dbp5p may play a role in unloading or remodeling messenger RNA particles (mRNPs) upon arrival in the cytoplasm and in coupling mRNP export and translation. The functions of Dbp5p are likely to be conserved, since its potential homologues can be found in a variety of eukaryotic cells.

Nonviable Staphylococcus aureus and its peptidoglycan stimulate macrophage recruitment, angiogenesis, fibroplasia, and collagen accumulation in wounded rats

We have previously shown that local application at the time of operation of Staphylococcus aureus, nonviable S. aureus, its cell wall, or S. aureus peptidoglycan accelerates wound healing. We hypothesized that this effect is due to both direct and indirect mechanisms, among which is an increase in the inflammatory response to wounding, resulting in an increase in macrophages, angiogenesis, and fibroblasts. Twenty-seven Sprague-Dawley male rats were anesthetized, and two 7-cm paravertebral skin incisions were made. Four polyvinyl alcohol sponges, two on each side, containing either 100 microliter of isotonic saline or 0.5 mg of nonviable S. aureus or S. aureus peptidoglycan in 100-microliter saline were implanted subcutaneously. Nonviable S. aureus or S. aureus peptidoglycan (860 microgram/cm incision) in 200-microliter saline were inoculated into the incisions at closure. The rats ate a commercial rat chow and drank tap water ad libitum throughout. After days 3 and 7 postwounding, rats were euthanized, and tissues were examined for immunohistochemical features of reparative tissue using ED-1, Factor VIII, and vimentin antibodies, markers for monocyte/macrophages, endothelial cells, and mesenchymal cells (including fibroblasts), respectively. Incisions treated with nonviable S. aureus or S. aureus peptidoglycan showed more macrophages along and deep in the wound tract 7 days postoperatively. Nonviable S. aureus or S. aureus peptidoglycan-treated sponges were surrounded and penetrated by much larger capsules of reparative tissue than saline-treated sponges at both 3 and 7 days. Neutrophil influx was much greater in nonviable S. aureus or S. aureus peptidoglycan-treated sponges, especially in central regions, and there were many more ED-1-stained macrophages in distinct geographic locations, specifically, the more peripheral-cortical areas. Some clustering of macrophages occurred around areas of invasion by reparative tissue into the surrounding subcutaneous fat and within the interstices of the sponges at the interface between reparative tissue and acute inflammatory cells. In contrast, saline-treated sponge reparative tissue had significantly fewer macrophages, much thinner and flimsy reparative tissue, with proportionately fewer macrophages clustering centrally. There were many more mesenchymal cells (notably fibroblasts) and new blood vessels and much more reparative collagen in the nonviable S. aureus or S. aureus peptidoglycan-treated sponges. We conclude that local application of nonviable S. aureus or S. aureus peptidoglycan at wounding induces an increased number and alteration in location of macrophages, increased influx (or proliferation) of mesenchymal cells (notably fibroblasts), and increased angiogenesis and reparative collagen accumulation, as well as increasing the overall acute inflammatory response to wounding.

Stimulation of endothelial cell production of vasoconstrictive substances by hypertensive sera

The endothelial cell regulates vessel tone by elaborating a number of vasoactive substances such as thromboxane and endothelin, both of which are highly vaosconstrictive, and prostacyclin and nitric oxide, both of which are vasodilatory. The current study examines the postulate that one of the mechanisms responsible for the increased vessel tone found in hypertension is the presence of substances in the sera of patients with this disorder that stimulates selectively the endothelial cell production of thromboxane and endothelin. Sera from ten patients with mild hypertension and from 11 age-matched controls were incubated with human umbilical arterial endothelial cells and the concentrations of endothelin, thromboxane, prostacyclin, and nitric oxide produced by the cells was measured in the supernatant. The results of the assays showed that the amounts of thromboxane and endothelin produced by endothelial cells in response to stimulation by hypertensive sera were significantly higher than the amounts produced in response to control sera; in comparison, the amounts of prostacyclin and nitric oxide produced by the cells in response to either hypertensive sera or control sera were not significantly different. The findings suggest that a mechanism that may be responsible for the increased vascular tone found in hypertension is the presence of substances in hypertensive sera that stimulate endothelial cells selectively to produce increased amounts of the vasoconstrictive hormones, endothelin and thromboxane.

Effects of N-methyl berbamine on delayed outward potassium current in isolated rat hepatocytes

AIM

To study the effects of N-methyl berbamine (NMB) on the delayed outward potassium currents (Ik) in isolated rat hepatocytes.

METHODS

With patch-clamp techniques and whole-cell recording method, holding potential -50 mV, command potential +30 to +140 mV, duration 900 ms.

RESULTS

NMB reduced Ik in a concentration-dependent manner. When the concentrations of NMB were 20, 50, 400 nmol.L-1 and 50 mumol.L-1, the amplitude values of Ik were decreased to 3.6 +/- 0.4 (P > 0.05), 2.1 +/- 1.6 (P > 0.05), 3.7 +/- 1.6 (P < 0.05), 2.3 +/- 1.3 nA (P < 0.01) from 4.4 +/- 1.0 (n = 4), 2.5 +/- 1.8 (n = 4), 5.8 +/- 2.1 (n = 5), 4.6 +/- 1.3 (n = 6) nA of control, respectively. The inhibitory rates were 10%, 15%, 37%, and 51%, respectively.

CONCLUSION

NMB was a K+ channel inhibitor.

The human papillomavirus-16 E6 oncoprotein decreases the vigilance of mitotic checkpoints

The E6 and E7 proteins of the high risk human papillomaviruses (HPVs) are consistently expressed in HPV-positive cervical carcinomas. We investigated the ability of HPV-16 E6 and E7 to disrupt mitotic checkpoints in normal diploid human cells. Acute expression of HPV-16 E6, but not HPV-16 E7, decreased the fidelity of multiple checkpoints controlling entry into and exit from mitosis. After irradiation, nearly 50% of cells containing HPV-16 E6 readily entered mitosis as opposed to less than 10% of control cells. Consistent with this, asynchronous populations of cells expressing HPV-16 E6 had increased cdc2-associated histone H1 kinase activity relative to control populations. In addition, HPV-16 E6 increased sensitivity to chemically-induced S-phase premature mitosis and decreased mitotic spindle assembly checkpoint function relative to control populations. HPV-16 E6 mutants with a reduced ability to target p53 for degradation were unable to abrogate mitotic checkpoints, suggesting a possible mechanism by which HPV-16 E6 disrupts mitotic checkpoints. Expression of a mutant p53 gene yielded an intermediate phenotype relative to HPV-16 E6, generating moderate increases in sensitivity to chemically-induced S-phase PCC and mitotic spindle disruption and a heightened propensity to enter mitosis after irradiation.

Genetic interactions of conserved regions in the DEAD-box protein Prp28p

The yeast PRP28 g ene has been implicated in nuclear precursor messenger RNA (pre-mRNA) splicing, a two-step reaction involved in a multitude of RNA structural alterations. Prp28p, the gene product of PRP28 , is a member of the evolutionarily conserved DEAD-box proteins (DBPs). Members of DBPs are involved in a variety of RNA-related biochemical processes, presumably by their putative RNA helicase activities. Prp28p has been speculated to play a role in melting the duplex between U4 and U6 small nuclear RNAs (snRNAs), leading to the formation of an active spliceosome. To study the function of Prp28p and its interactions with other components of the splicing machinery, we have isolated and characterized a large number of prp28 conditional mutants. Strikingly, many of these prp28 mutations are localized in the highly conserved motifs found in all the DBPs. Intragenic reversion analysis suggests that regions of motifs II, III and V, as well as of motifs I and IV, in Prp28p are likely to be in close proximity to each other. Our results thus provide the first hint of the local structural arrangement for Prp28p, and perhaps for other DBPs as well.